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What is clustering?
Wikipedia: Cluster analysis or clustering is the task of grouping a set of objects in such a way that objects in the same group (called a cluster) are more similar (in some sense or another) to each other than to those in other groups (clusters).
Generally speaking, clustering is NP-hard, so it is difficult to identify a provable optimal clustering.
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Given two vectors $u = (0,1)$ and $v = (2,0)$
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Given two vectors $u = (0,1)$ and $v = (2,0)$
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Given two vectors $u = (0,1)$ and $v = (2,0)$
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import scipy.spatial.distance
help(scipy.spatial.distance)
Help on module scipy.spatial.distance in scipy.spatial: NAME scipy.spatial.distance DESCRIPTION Distance computations (:mod:`scipy.spatial.distance`) ===================================================== .. sectionauthor:: Damian Eads Function reference ------------------ Distance matrix computation from a collection of raw observation vectors stored in a rectangular array. .. autosummary:: :toctree: generated/ pdist -- pairwise distances between observation vectors. cdist -- distances between two collections of observation vectors squareform -- convert distance matrix to a condensed one and vice versa directed_hausdorff -- directed Hausdorff distance between arrays Predicates for checking the validity of distance matrices, both condensed and redundant. Also contained in this module are functions for computing the number of observations in a distance matrix. .. autosummary:: :toctree: generated/ is_valid_dm -- checks for a valid distance matrix is_valid_y -- checks for a valid condensed distance matrix num_obs_dm -- # of observations in a distance matrix num_obs_y -- # of observations in a condensed distance matrix Distance functions between two numeric vectors ``u`` and ``v``. Computing distances over a large collection of vectors is inefficient for these functions. Use ``pdist`` for this purpose. .. autosummary:: :toctree: generated/ braycurtis -- the Bray-Curtis distance. canberra -- the Canberra distance. chebyshev -- the Chebyshev distance. cityblock -- the Manhattan distance. correlation -- the Correlation distance. cosine -- the Cosine distance. euclidean -- the Euclidean distance. jensenshannon -- the Jensen-Shannon distance. mahalanobis -- the Mahalanobis distance. minkowski -- the Minkowski distance. seuclidean -- the normalized Euclidean distance. sqeuclidean -- the squared Euclidean distance. Distance functions between two boolean vectors (representing sets) ``u`` and ``v``. As in the case of numerical vectors, ``pdist`` is more efficient for computing the distances between all pairs. .. autosummary:: :toctree: generated/ dice -- the Dice dissimilarity. hamming -- the Hamming distance. jaccard -- the Jaccard distance. kulczynski1 -- the Kulczynski 1 distance. rogerstanimoto -- the Rogers-Tanimoto dissimilarity. russellrao -- the Russell-Rao dissimilarity. sokalmichener -- the Sokal-Michener dissimilarity. sokalsneath -- the Sokal-Sneath dissimilarity. yule -- the Yule dissimilarity. :func:`hamming` also operates over discrete numerical vectors. FUNCTIONS braycurtis(u, v, w=None) Compute the Bray-Curtis distance between two 1-D arrays. Bray-Curtis distance is defined as .. math:: \sum{|u_i-v_i|} / \sum{|u_i+v_i|} The Bray-Curtis distance is in the range [0, 1] if all coordinates are positive, and is undefined if the inputs are of length zero. Parameters ---------- u : (N,) array_like Input array. v : (N,) array_like Input array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- braycurtis : double The Bray-Curtis distance between 1-D arrays `u` and `v`. Examples -------- >>> from scipy.spatial import distance >>> distance.braycurtis([1, 0, 0], [0, 1, 0]) 1.0 >>> distance.braycurtis([1, 1, 0], [0, 1, 0]) 0.33333333333333331 canberra(u, v, w=None) Compute the Canberra distance between two 1-D arrays. The Canberra distance is defined as .. math:: d(u,v) = \sum_i \frac{|u_i-v_i|} {|u_i|+|v_i|}. Parameters ---------- u : (N,) array_like Input array. v : (N,) array_like Input array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- canberra : double The Canberra distance between vectors `u` and `v`. Notes ----- When `u[i]` and `v[i]` are 0 for given i, then the fraction 0/0 = 0 is used in the calculation. Examples -------- >>> from scipy.spatial import distance >>> distance.canberra([1, 0, 0], [0, 1, 0]) 2.0 >>> distance.canberra([1, 1, 0], [0, 1, 0]) 1.0 cdist(XA, XB, metric='euclidean', *, out=None, **kwargs) Compute distance between each pair of the two collections of inputs. See Notes for common calling conventions. Parameters ---------- XA : array_like An :math:`m_A` by :math:`n` array of :math:`m_A` original observations in an :math:`n`-dimensional space. Inputs are converted to float type. XB : array_like An :math:`m_B` by :math:`n` array of :math:`m_B` original observations in an :math:`n`-dimensional space. Inputs are converted to float type. metric : str or callable, optional The distance metric to use. If a string, the distance function can be 'braycurtis', 'canberra', 'chebyshev', 'cityblock', 'correlation', 'cosine', 'dice', 'euclidean', 'hamming', 'jaccard', 'jensenshannon', 'kulczynski1', 'mahalanobis', 'matching', 'minkowski', 'rogerstanimoto', 'russellrao', 'seuclidean', 'sokalmichener', 'sokalsneath', 'sqeuclidean', 'yule'. **kwargs : dict, optional Extra arguments to `metric`: refer to each metric documentation for a list of all possible arguments. Some possible arguments: p : scalar The p-norm to apply for Minkowski, weighted and unweighted. Default: 2. w : array_like The weight vector for metrics that support weights (e.g., Minkowski). V : array_like The variance vector for standardized Euclidean. Default: var(vstack([XA, XB]), axis=0, ddof=1) VI : array_like The inverse of the covariance matrix for Mahalanobis. Default: inv(cov(vstack([XA, XB].T))).T out : ndarray The output array If not None, the distance matrix Y is stored in this array. Returns ------- Y : ndarray A :math:`m_A` by :math:`m_B` distance matrix is returned. For each :math:`i` and :math:`j`, the metric ``dist(u=XA[i], v=XB[j])`` is computed and stored in the :math:`ij` th entry. Raises ------ ValueError An exception is thrown if `XA` and `XB` do not have the same number of columns. Notes ----- The following are common calling conventions: 1. ``Y = cdist(XA, XB, 'euclidean')`` Computes the distance between :math:`m` points using Euclidean distance (2-norm) as the distance metric between the points. The points are arranged as :math:`m` :math:`n`-dimensional row vectors in the matrix X. 2. ``Y = cdist(XA, XB, 'minkowski', p=2.)`` Computes the distances using the Minkowski distance :math:`\|u-v\|_p` (:math:`p`-norm) where :math:`p > 0` (note that this is only a quasi-metric if :math:`0 < p < 1`). 3. ``Y = cdist(XA, XB, 'cityblock')`` Computes the city block or Manhattan distance between the points. 4. ``Y = cdist(XA, XB, 'seuclidean', V=None)`` Computes the standardized Euclidean distance. The standardized Euclidean distance between two n-vectors ``u`` and ``v`` is .. math:: \sqrt{\sum {(u_i-v_i)^2 / V[x_i]}}. V is the variance vector; V[i] is the variance computed over all the i'th components of the points. If not passed, it is automatically computed. 5. ``Y = cdist(XA, XB, 'sqeuclidean')`` Computes the squared Euclidean distance :math:`\|u-v\|_2^2` between the vectors. 6. ``Y = cdist(XA, XB, 'cosine')`` Computes the cosine distance between vectors u and v, .. math:: 1 - \frac{u \cdot v} {{\|u\|}_2 {\|v\|}_2} where :math:`\|*\|_2` is the 2-norm of its argument ``*``, and :math:`u \cdot v` is the dot product of :math:`u` and :math:`v`. 7. ``Y = cdist(XA, XB, 'correlation')`` Computes the correlation distance between vectors u and v. This is .. math:: 1 - \frac{(u - \bar{u}) \cdot (v - \bar{v})} {{\|(u - \bar{u})\|}_2 {\|(v - \bar{v})\|}_2} where :math:`\bar{v}` is the mean of the elements of vector v, and :math:`x \cdot y` is the dot product of :math:`x` and :math:`y`. 8. ``Y = cdist(XA, XB, 'hamming')`` Computes the normalized Hamming distance, or the proportion of those vector elements between two n-vectors ``u`` and ``v`` which disagree. To save memory, the matrix ``X`` can be of type boolean. 9. ``Y = cdist(XA, XB, 'jaccard')`` Computes the Jaccard distance between the points. Given two vectors, ``u`` and ``v``, the Jaccard distance is the proportion of those elements ``u[i]`` and ``v[i]`` that disagree where at least one of them is non-zero. 10. ``Y = cdist(XA, XB, 'jensenshannon')`` Computes the Jensen-Shannon distance between two probability arrays. Given two probability vectors, :math:`p` and :math:`q`, the Jensen-Shannon distance is .. math:: \sqrt{\frac{D(p \parallel m) + D(q \parallel m)}{2}} where :math:`m` is the pointwise mean of :math:`p` and :math:`q` and :math:`D` is the Kullback-Leibler divergence. 11. ``Y = cdist(XA, XB, 'chebyshev')`` Computes the Chebyshev distance between the points. The Chebyshev distance between two n-vectors ``u`` and ``v`` is the maximum norm-1 distance between their respective elements. More precisely, the distance is given by .. math:: d(u,v) = \max_i {|u_i-v_i|}. 12. ``Y = cdist(XA, XB, 'canberra')`` Computes the Canberra distance between the points. The Canberra distance between two points ``u`` and ``v`` is .. math:: d(u,v) = \sum_i \frac{|u_i-v_i|} {|u_i|+|v_i|}. 13. ``Y = cdist(XA, XB, 'braycurtis')`` Computes the Bray-Curtis distance between the points. The Bray-Curtis distance between two points ``u`` and ``v`` is .. math:: d(u,v) = \frac{\sum_i (|u_i-v_i|)} {\sum_i (|u_i+v_i|)} 14. ``Y = cdist(XA, XB, 'mahalanobis', VI=None)`` Computes the Mahalanobis distance between the points. The Mahalanobis distance between two points ``u`` and ``v`` is :math:`\sqrt{(u-v)(1/V)(u-v)^T}` where :math:`(1/V)` (the ``VI`` variable) is the inverse covariance. If ``VI`` is not None, ``VI`` will be used as the inverse covariance matrix. 15. ``Y = cdist(XA, XB, 'yule')`` Computes the Yule distance between the boolean vectors. (see `yule` function documentation) 16. ``Y = cdist(XA, XB, 'matching')`` Synonym for 'hamming'. 17. ``Y = cdist(XA, XB, 'dice')`` Computes the Dice distance between the boolean vectors. (see `dice` function documentation) 18. ``Y = cdist(XA, XB, 'kulczynski1')`` Computes the kulczynski distance between the boolean vectors. (see `kulczynski1` function documentation) 19. ``Y = cdist(XA, XB, 'rogerstanimoto')`` Computes the Rogers-Tanimoto distance between the boolean vectors. (see `rogerstanimoto` function documentation) 20. ``Y = cdist(XA, XB, 'russellrao')`` Computes the Russell-Rao distance between the boolean vectors. (see `russellrao` function documentation) 21. ``Y = cdist(XA, XB, 'sokalmichener')`` Computes the Sokal-Michener distance between the boolean vectors. (see `sokalmichener` function documentation) 22. ``Y = cdist(XA, XB, 'sokalsneath')`` Computes the Sokal-Sneath distance between the vectors. (see `sokalsneath` function documentation) 23. ``Y = cdist(XA, XB, f)`` Computes the distance between all pairs of vectors in X using the user supplied 2-arity function f. For example, Euclidean distance between the vectors could be computed as follows:: dm = cdist(XA, XB, lambda u, v: np.sqrt(((u-v)**2).sum())) Note that you should avoid passing a reference to one of the distance functions defined in this library. For example,:: dm = cdist(XA, XB, sokalsneath) would calculate the pair-wise distances between the vectors in X using the Python function `sokalsneath`. This would result in sokalsneath being called :math:`{n \choose 2}` times, which is inefficient. Instead, the optimized C version is more efficient, and we call it using the following syntax:: dm = cdist(XA, XB, 'sokalsneath') Examples -------- Find the Euclidean distances between four 2-D coordinates: >>> from scipy.spatial import distance >>> import numpy as np >>> coords = [(35.0456, -85.2672), ... (35.1174, -89.9711), ... (35.9728, -83.9422), ... (36.1667, -86.7833)] >>> distance.cdist(coords, coords, 'euclidean') array([[ 0. , 4.7044, 1.6172, 1.8856], [ 4.7044, 0. , 6.0893, 3.3561], [ 1.6172, 6.0893, 0. , 2.8477], [ 1.8856, 3.3561, 2.8477, 0. ]]) Find the Manhattan distance from a 3-D point to the corners of the unit cube: >>> a = np.array([[0, 0, 0], ... [0, 0, 1], ... [0, 1, 0], ... [0, 1, 1], ... [1, 0, 0], ... [1, 0, 1], ... [1, 1, 0], ... [1, 1, 1]]) >>> b = np.array([[ 0.1, 0.2, 0.4]]) >>> distance.cdist(a, b, 'cityblock') array([[ 0.7], [ 0.9], [ 1.3], [ 1.5], [ 1.5], [ 1.7], [ 2.1], [ 2.3]]) chebyshev(u, v, w=None) Compute the Chebyshev distance. Computes the Chebyshev distance between two 1-D arrays `u` and `v`, which is defined as .. math:: \max_i {|u_i-v_i|}. Parameters ---------- u : (N,) array_like Input vector. v : (N,) array_like Input vector. w : (N,) array_like, optional Unused, as 'max' is a weightless operation. Here for API consistency. Returns ------- chebyshev : double The Chebyshev distance between vectors `u` and `v`. Examples -------- >>> from scipy.spatial import distance >>> distance.chebyshev([1, 0, 0], [0, 1, 0]) 1 >>> distance.chebyshev([1, 1, 0], [0, 1, 0]) 1 cityblock(u, v, w=None) Compute the City Block (Manhattan) distance. Computes the Manhattan distance between two 1-D arrays `u` and `v`, which is defined as .. math:: \sum_i {\left| u_i - v_i \right|}. Parameters ---------- u : (N,) array_like Input array. v : (N,) array_like Input array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- cityblock : double The City Block (Manhattan) distance between vectors `u` and `v`. Examples -------- >>> from scipy.spatial import distance >>> distance.cityblock([1, 0, 0], [0, 1, 0]) 2 >>> distance.cityblock([1, 0, 0], [0, 2, 0]) 3 >>> distance.cityblock([1, 0, 0], [1, 1, 0]) 1 correlation(u, v, w=None, centered=True) Compute the correlation distance between two 1-D arrays. The correlation distance between `u` and `v`, is defined as .. math:: 1 - \frac{(u - \bar{u}) \cdot (v - \bar{v})} {{\|(u - \bar{u})\|}_2 {\|(v - \bar{v})\|}_2} where :math:`\bar{u}` is the mean of the elements of `u` and :math:`x \cdot y` is the dot product of :math:`x` and :math:`y`. Parameters ---------- u : (N,) array_like Input array. v : (N,) array_like Input array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 centered : bool, optional If True, `u` and `v` will be centered. Default is True. Returns ------- correlation : double The correlation distance between 1-D array `u` and `v`. cosine(u, v, w=None) Compute the Cosine distance between 1-D arrays. The Cosine distance between `u` and `v`, is defined as .. math:: 1 - \frac{u \cdot v} {\|u\|_2 \|v\|_2}. where :math:`u \cdot v` is the dot product of :math:`u` and :math:`v`. Parameters ---------- u : (N,) array_like Input array. v : (N,) array_like Input array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- cosine : double The Cosine distance between vectors `u` and `v`. Examples -------- >>> from scipy.spatial import distance >>> distance.cosine([1, 0, 0], [0, 1, 0]) 1.0 >>> distance.cosine([100, 0, 0], [0, 1, 0]) 1.0 >>> distance.cosine([1, 1, 0], [0, 1, 0]) 0.29289321881345254 dice(u, v, w=None) Compute the Dice dissimilarity between two boolean 1-D arrays. The Dice dissimilarity between `u` and `v`, is .. math:: \frac{c_{TF} + c_{FT}} {2c_{TT} + c_{FT} + c_{TF}} where :math:`c_{ij}` is the number of occurrences of :math:`\mathtt{u[k]} = i` and :math:`\mathtt{v[k]} = j` for :math:`k < n`. Parameters ---------- u : (N,) array_like, bool Input 1-D array. v : (N,) array_like, bool Input 1-D array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- dice : double The Dice dissimilarity between 1-D arrays `u` and `v`. Notes ----- This function computes the Dice dissimilarity index. To compute the Dice similarity index, convert one to the other with similarity = 1 - dissimilarity. Examples -------- >>> from scipy.spatial import distance >>> distance.dice([1, 0, 0], [0, 1, 0]) 1.0 >>> distance.dice([1, 0, 0], [1, 1, 0]) 0.3333333333333333 >>> distance.dice([1, 0, 0], [2, 0, 0]) -0.3333333333333333 directed_hausdorff(u, v, seed=0) Compute the directed Hausdorff distance between two 2-D arrays. Distances between pairs are calculated using a Euclidean metric. Parameters ---------- u : (M,N) array_like Input array. v : (O,N) array_like Input array. seed : int or None Local `numpy.random.RandomState` seed. Default is 0, a random shuffling of u and v that guarantees reproducibility. Returns ------- d : double The directed Hausdorff distance between arrays `u` and `v`, index_1 : int index of point contributing to Hausdorff pair in `u` index_2 : int index of point contributing to Hausdorff pair in `v` Raises ------ ValueError An exception is thrown if `u` and `v` do not have the same number of columns. See Also -------- scipy.spatial.procrustes : Another similarity test for two data sets Notes ----- Uses the early break technique and the random sampling approach described by [1]_. Although worst-case performance is ``O(m * o)`` (as with the brute force algorithm), this is unlikely in practice as the input data would have to require the algorithm to explore every single point interaction, and after the algorithm shuffles the input points at that. The best case performance is O(m), which is satisfied by selecting an inner loop distance that is less than cmax and leads to an early break as often as possible. The authors have formally shown that the average runtime is closer to O(m). .. versionadded:: 0.19.0 References ---------- .. [1] A. A. Taha and A. Hanbury, "An efficient algorithm for calculating the exact Hausdorff distance." IEEE Transactions On Pattern Analysis And Machine Intelligence, vol. 37 pp. 2153-63, 2015. Examples -------- Find the directed Hausdorff distance between two 2-D arrays of coordinates: >>> from scipy.spatial.distance import directed_hausdorff >>> import numpy as np >>> u = np.array([(1.0, 0.0), ... (0.0, 1.0), ... (-1.0, 0.0), ... (0.0, -1.0)]) >>> v = np.array([(2.0, 0.0), ... (0.0, 2.0), ... (-2.0, 0.0), ... (0.0, -4.0)]) >>> directed_hausdorff(u, v)[0] 2.23606797749979 >>> directed_hausdorff(v, u)[0] 3.0 Find the general (symmetric) Hausdorff distance between two 2-D arrays of coordinates: >>> max(directed_hausdorff(u, v)[0], directed_hausdorff(v, u)[0]) 3.0 Find the indices of the points that generate the Hausdorff distance (the Hausdorff pair): >>> directed_hausdorff(v, u)[1:] (3, 3) euclidean(u, v, w=None) Computes the Euclidean distance between two 1-D arrays. The Euclidean distance between 1-D arrays `u` and `v`, is defined as .. math:: {\|u-v\|}_2 \left(\sum{(w_i |(u_i - v_i)|^2)}\right)^{1/2} Parameters ---------- u : (N,) array_like Input array. v : (N,) array_like Input array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- euclidean : double The Euclidean distance between vectors `u` and `v`. Examples -------- >>> from scipy.spatial import distance >>> distance.euclidean([1, 0, 0], [0, 1, 0]) 1.4142135623730951 >>> distance.euclidean([1, 1, 0], [0, 1, 0]) 1.0 hamming(u, v, w=None) Compute the Hamming distance between two 1-D arrays. The Hamming distance between 1-D arrays `u` and `v`, is simply the proportion of disagreeing components in `u` and `v`. If `u` and `v` are boolean vectors, the Hamming distance is .. math:: \frac{c_{01} + c_{10}}{n} where :math:`c_{ij}` is the number of occurrences of :math:`\mathtt{u[k]} = i` and :math:`\mathtt{v[k]} = j` for :math:`k < n`. Parameters ---------- u : (N,) array_like Input array. v : (N,) array_like Input array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- hamming : double The Hamming distance between vectors `u` and `v`. Examples -------- >>> from scipy.spatial import distance >>> distance.hamming([1, 0, 0], [0, 1, 0]) 0.66666666666666663 >>> distance.hamming([1, 0, 0], [1, 1, 0]) 0.33333333333333331 >>> distance.hamming([1, 0, 0], [2, 0, 0]) 0.33333333333333331 >>> distance.hamming([1, 0, 0], [3, 0, 0]) 0.33333333333333331 is_valid_dm(D, tol=0.0, throw=False, name='D', warning=False) Return True if input array is a valid distance matrix. Distance matrices must be 2-dimensional numpy arrays. They must have a zero-diagonal, and they must be symmetric. Parameters ---------- D : array_like The candidate object to test for validity. tol : float, optional The distance matrix should be symmetric. `tol` is the maximum difference between entries ``ij`` and ``ji`` for the distance metric to be considered symmetric. throw : bool, optional An exception is thrown if the distance matrix passed is not valid. name : str, optional The name of the variable to checked. This is useful if throw is set to True so the offending variable can be identified in the exception message when an exception is thrown. warning : bool, optional Instead of throwing an exception, a warning message is raised. Returns ------- valid : bool True if the variable `D` passed is a valid distance matrix. Notes ----- Small numerical differences in `D` and `D.T` and non-zeroness of the diagonal are ignored if they are within the tolerance specified by `tol`. Examples -------- >>> import numpy as np >>> from scipy.spatial.distance import is_valid_dm This matrix is a valid distance matrix. >>> d = np.array([[0.0, 1.1, 1.2, 1.3], ... [1.1, 0.0, 1.0, 1.4], ... [1.2, 1.0, 0.0, 1.5], ... [1.3, 1.4, 1.5, 0.0]]) >>> is_valid_dm(d) True In the following examples, the input is not a valid distance matrix. Not square: >>> is_valid_dm([[0, 2, 2], [2, 0, 2]]) False Nonzero diagonal element: >>> is_valid_dm([[0, 1, 1], [1, 2, 3], [1, 3, 0]]) False Not symmetric: >>> is_valid_dm([[0, 1, 3], [2, 0, 1], [3, 1, 0]]) False is_valid_y(y, warning=False, throw=False, name=None) Return True if the input array is a valid condensed distance matrix. Condensed distance matrices must be 1-dimensional numpy arrays. Their length must be a binomial coefficient :math:`{n \choose 2}` for some positive integer n. Parameters ---------- y : array_like The condensed distance matrix. warning : bool, optional Invokes a warning if the variable passed is not a valid condensed distance matrix. The warning message explains why the distance matrix is not valid. `name` is used when referencing the offending variable. throw : bool, optional Throws an exception if the variable passed is not a valid condensed distance matrix. name : bool, optional Used when referencing the offending variable in the warning or exception message. Returns ------- bool True if the input array is a valid condensed distance matrix, False otherwise. Examples -------- >>> from scipy.spatial.distance import is_valid_y This vector is a valid condensed distance matrix. The length is 6, which corresponds to ``n = 4``, since ``4*(4 - 1)/2`` is 6. >>> v = [1.0, 1.2, 1.0, 0.5, 1.3, 0.9] >>> is_valid_y(v) True An input vector with length, say, 7, is not a valid condensed distance matrix. >>> is_valid_y([1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7]) False jaccard(u, v, w=None) Compute the Jaccard-Needham dissimilarity between two boolean 1-D arrays. The Jaccard-Needham dissimilarity between 1-D boolean arrays `u` and `v`, is defined as .. math:: \frac{c_{TF} + c_{FT}} {c_{TT} + c_{FT} + c_{TF}} where :math:`c_{ij}` is the number of occurrences of :math:`\mathtt{u[k]} = i` and :math:`\mathtt{v[k]} = j` for :math:`k < n`. Parameters ---------- u : (N,) array_like, bool Input array. v : (N,) array_like, bool Input array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- jaccard : double The Jaccard distance between vectors `u` and `v`. Notes ----- When both `u` and `v` lead to a `0/0` division i.e. there is no overlap between the items in the vectors the returned distance is 0. See the Wikipedia page on the Jaccard index [1]_, and this paper [2]_. .. versionchanged:: 1.2.0 Previously, when `u` and `v` lead to a `0/0` division, the function would return NaN. This was changed to return 0 instead. References ---------- .. [1] https://en.wikipedia.org/wiki/Jaccard_index .. [2] S. Kosub, "A note on the triangle inequality for the Jaccard distance", 2016, :arxiv:`1612.02696` Examples -------- >>> from scipy.spatial import distance >>> distance.jaccard([1, 0, 0], [0, 1, 0]) 1.0 >>> distance.jaccard([1, 0, 0], [1, 1, 0]) 0.5 >>> distance.jaccard([1, 0, 0], [1, 2, 0]) 0.5 >>> distance.jaccard([1, 0, 0], [1, 1, 1]) 0.66666666666666663 jensenshannon(p, q, base=None, *, axis=0, keepdims=False) Compute the Jensen-Shannon distance (metric) between two probability arrays. This is the square root of the Jensen-Shannon divergence. The Jensen-Shannon distance between two probability vectors `p` and `q` is defined as, .. math:: \sqrt{\frac{D(p \parallel m) + D(q \parallel m)}{2}} where :math:`m` is the pointwise mean of :math:`p` and :math:`q` and :math:`D` is the Kullback-Leibler divergence. This routine will normalize `p` and `q` if they don't sum to 1.0. Parameters ---------- p : (N,) array_like left probability vector q : (N,) array_like right probability vector base : double, optional the base of the logarithm used to compute the output if not given, then the routine uses the default base of scipy.stats.entropy. axis : int, optional Axis along which the Jensen-Shannon distances are computed. The default is 0. .. versionadded:: 1.7.0 keepdims : bool, optional If this is set to `True`, the reduced axes are left in the result as dimensions with size one. With this option, the result will broadcast correctly against the input array. Default is False. .. versionadded:: 1.7.0 Returns ------- js : double or ndarray The Jensen-Shannon distances between `p` and `q` along the `axis`. Notes ----- .. versionadded:: 1.2.0 Examples -------- >>> from scipy.spatial import distance >>> import numpy as np >>> distance.jensenshannon([1.0, 0.0, 0.0], [0.0, 1.0, 0.0], 2.0) 1.0 >>> distance.jensenshannon([1.0, 0.0], [0.5, 0.5]) 0.46450140402245893 >>> distance.jensenshannon([1.0, 0.0, 0.0], [1.0, 0.0, 0.0]) 0.0 >>> a = np.array([[1, 2, 3, 4], ... [5, 6, 7, 8], ... [9, 10, 11, 12]]) >>> b = np.array([[13, 14, 15, 16], ... [17, 18, 19, 20], ... [21, 22, 23, 24]]) >>> distance.jensenshannon(a, b, axis=0) array([0.1954288, 0.1447697, 0.1138377, 0.0927636]) >>> distance.jensenshannon(a, b, axis=1) array([0.1402339, 0.0399106, 0.0201815]) kulczynski1(u, v, *, w=None) Compute the Kulczynski 1 dissimilarity between two boolean 1-D arrays. The Kulczynski 1 dissimilarity between two boolean 1-D arrays `u` and `v` of length ``n``, is defined as .. math:: \frac{c_{11}} {c_{01} + c_{10}} where :math:`c_{ij}` is the number of occurrences of :math:`\mathtt{u[k]} = i` and :math:`\mathtt{v[k]} = j` for :math:`k \in {0, 1, ..., n-1}`. Parameters ---------- u : (N,) array_like, bool Input array. v : (N,) array_like, bool Input array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- kulczynski1 : float The Kulczynski 1 distance between vectors `u` and `v`. Notes ----- This measure has a minimum value of 0 and no upper limit. It is un-defined when there are no non-matches. .. versionadded:: 1.8.0 References ---------- .. [1] Kulczynski S. et al. Bulletin International de l'Academie Polonaise des Sciences et des Lettres, Classe des Sciences Mathematiques et Naturelles, Serie B (Sciences Naturelles). 1927; Supplement II: 57-203. Examples -------- >>> from scipy.spatial import distance >>> distance.kulczynski1([1, 0, 0], [0, 1, 0]) 0.0 >>> distance.kulczynski1([True, False, False], [True, True, False]) 1.0 >>> distance.kulczynski1([True, False, False], [True]) 0.5 >>> distance.kulczynski1([1, 0, 0], [3, 1, 0]) -3.0 mahalanobis(u, v, VI) Compute the Mahalanobis distance between two 1-D arrays. The Mahalanobis distance between 1-D arrays `u` and `v`, is defined as .. math:: \sqrt{ (u-v) V^{-1} (u-v)^T } where ``V`` is the covariance matrix. Note that the argument `VI` is the inverse of ``V``. Parameters ---------- u : (N,) array_like Input array. v : (N,) array_like Input array. VI : array_like The inverse of the covariance matrix. Returns ------- mahalanobis : double The Mahalanobis distance between vectors `u` and `v`. Examples -------- >>> from scipy.spatial import distance >>> iv = [[1, 0.5, 0.5], [0.5, 1, 0.5], [0.5, 0.5, 1]] >>> distance.mahalanobis([1, 0, 0], [0, 1, 0], iv) 1.0 >>> distance.mahalanobis([0, 2, 0], [0, 1, 0], iv) 1.0 >>> distance.mahalanobis([2, 0, 0], [0, 1, 0], iv) 1.7320508075688772 minkowski(u, v, p=2, w=None) Compute the Minkowski distance between two 1-D arrays. The Minkowski distance between 1-D arrays `u` and `v`, is defined as .. math:: {\|u-v\|}_p = (\sum{|u_i - v_i|^p})^{1/p}. \left(\sum{w_i(|(u_i - v_i)|^p)}\right)^{1/p}. Parameters ---------- u : (N,) array_like Input array. v : (N,) array_like Input array. p : scalar The order of the norm of the difference :math:`{\|u-v\|}_p`. Note that for :math:`0 < p < 1`, the triangle inequality only holds with an additional multiplicative factor, i.e. it is only a quasi-metric. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- minkowski : double The Minkowski distance between vectors `u` and `v`. Examples -------- >>> from scipy.spatial import distance >>> distance.minkowski([1, 0, 0], [0, 1, 0], 1) 2.0 >>> distance.minkowski([1, 0, 0], [0, 1, 0], 2) 1.4142135623730951 >>> distance.minkowski([1, 0, 0], [0, 1, 0], 3) 1.2599210498948732 >>> distance.minkowski([1, 1, 0], [0, 1, 0], 1) 1.0 >>> distance.minkowski([1, 1, 0], [0, 1, 0], 2) 1.0 >>> distance.minkowski([1, 1, 0], [0, 1, 0], 3) 1.0 num_obs_dm(d) Return the number of original observations that correspond to a square, redundant distance matrix. Parameters ---------- d : array_like The target distance matrix. Returns ------- num_obs_dm : int The number of observations in the redundant distance matrix. num_obs_y(Y) Return the number of original observations that correspond to a condensed distance matrix. Parameters ---------- Y : array_like Condensed distance matrix. Returns ------- n : int The number of observations in the condensed distance matrix `Y`. pdist(X, metric='euclidean', *, out=None, **kwargs) Pairwise distances between observations in n-dimensional space. See Notes for common calling conventions. Parameters ---------- X : array_like An m by n array of m original observations in an n-dimensional space. metric : str or function, optional The distance metric to use. The distance function can be 'braycurtis', 'canberra', 'chebyshev', 'cityblock', 'correlation', 'cosine', 'dice', 'euclidean', 'hamming', 'jaccard', 'jensenshannon', 'kulczynski1', 'mahalanobis', 'matching', 'minkowski', 'rogerstanimoto', 'russellrao', 'seuclidean', 'sokalmichener', 'sokalsneath', 'sqeuclidean', 'yule'. out : ndarray The output array. If not None, condensed distance matrix Y is stored in this array. **kwargs : dict, optional Extra arguments to `metric`: refer to each metric documentation for a list of all possible arguments. Some possible arguments: p : scalar The p-norm to apply for Minkowski, weighted and unweighted. Default: 2. w : ndarray The weight vector for metrics that support weights (e.g., Minkowski). V : ndarray The variance vector for standardized Euclidean. Default: var(X, axis=0, ddof=1) VI : ndarray The inverse of the covariance matrix for Mahalanobis. Default: inv(cov(X.T)).T Returns ------- Y : ndarray Returns a condensed distance matrix Y. For each :math:`i` and :math:`j` (where :math:`i<j<m`),where m is the number of original observations. The metric ``dist(u=X[i], v=X[j])`` is computed and stored in entry ``m * i + j - ((i + 2) * (i + 1)) // 2``. See Also -------- squareform : converts between condensed distance matrices and square distance matrices. Notes ----- See ``squareform`` for information on how to calculate the index of this entry or to convert the condensed distance matrix to a redundant square matrix. The following are common calling conventions. 1. ``Y = pdist(X, 'euclidean')`` Computes the distance between m points using Euclidean distance (2-norm) as the distance metric between the points. The points are arranged as m n-dimensional row vectors in the matrix X. 2. ``Y = pdist(X, 'minkowski', p=2.)`` Computes the distances using the Minkowski distance :math:`\|u-v\|_p` (:math:`p`-norm) where :math:`p > 0` (note that this is only a quasi-metric if :math:`0 < p < 1`). 3. ``Y = pdist(X, 'cityblock')`` Computes the city block or Manhattan distance between the points. 4. ``Y = pdist(X, 'seuclidean', V=None)`` Computes the standardized Euclidean distance. The standardized Euclidean distance between two n-vectors ``u`` and ``v`` is .. math:: \sqrt{\sum {(u_i-v_i)^2 / V[x_i]}} V is the variance vector; V[i] is the variance computed over all the i'th components of the points. If not passed, it is automatically computed. 5. ``Y = pdist(X, 'sqeuclidean')`` Computes the squared Euclidean distance :math:`\|u-v\|_2^2` between the vectors. 6. ``Y = pdist(X, 'cosine')`` Computes the cosine distance between vectors u and v, .. math:: 1 - \frac{u \cdot v} {{\|u\|}_2 {\|v\|}_2} where :math:`\|*\|_2` is the 2-norm of its argument ``*``, and :math:`u \cdot v` is the dot product of ``u`` and ``v``. 7. ``Y = pdist(X, 'correlation')`` Computes the correlation distance between vectors u and v. This is .. math:: 1 - \frac{(u - \bar{u}) \cdot (v - \bar{v})} {{\|(u - \bar{u})\|}_2 {\|(v - \bar{v})\|}_2} where :math:`\bar{v}` is the mean of the elements of vector v, and :math:`x \cdot y` is the dot product of :math:`x` and :math:`y`. 8. ``Y = pdist(X, 'hamming')`` Computes the normalized Hamming distance, or the proportion of those vector elements between two n-vectors ``u`` and ``v`` which disagree. To save memory, the matrix ``X`` can be of type boolean. 9. ``Y = pdist(X, 'jaccard')`` Computes the Jaccard distance between the points. Given two vectors, ``u`` and ``v``, the Jaccard distance is the proportion of those elements ``u[i]`` and ``v[i]`` that disagree. 10. ``Y = pdist(X, 'jensenshannon')`` Computes the Jensen-Shannon distance between two probability arrays. Given two probability vectors, :math:`p` and :math:`q`, the Jensen-Shannon distance is .. math:: \sqrt{\frac{D(p \parallel m) + D(q \parallel m)}{2}} where :math:`m` is the pointwise mean of :math:`p` and :math:`q` and :math:`D` is the Kullback-Leibler divergence. 11. ``Y = pdist(X, 'chebyshev')`` Computes the Chebyshev distance between the points. The Chebyshev distance between two n-vectors ``u`` and ``v`` is the maximum norm-1 distance between their respective elements. More precisely, the distance is given by .. math:: d(u,v) = \max_i {|u_i-v_i|} 12. ``Y = pdist(X, 'canberra')`` Computes the Canberra distance between the points. The Canberra distance between two points ``u`` and ``v`` is .. math:: d(u,v) = \sum_i \frac{|u_i-v_i|} {|u_i|+|v_i|} 13. ``Y = pdist(X, 'braycurtis')`` Computes the Bray-Curtis distance between the points. The Bray-Curtis distance between two points ``u`` and ``v`` is .. math:: d(u,v) = \frac{\sum_i {|u_i-v_i|}} {\sum_i {|u_i+v_i|}} 14. ``Y = pdist(X, 'mahalanobis', VI=None)`` Computes the Mahalanobis distance between the points. The Mahalanobis distance between two points ``u`` and ``v`` is :math:`\sqrt{(u-v)(1/V)(u-v)^T}` where :math:`(1/V)` (the ``VI`` variable) is the inverse covariance. If ``VI`` is not None, ``VI`` will be used as the inverse covariance matrix. 15. ``Y = pdist(X, 'yule')`` Computes the Yule distance between each pair of boolean vectors. (see yule function documentation) 16. ``Y = pdist(X, 'matching')`` Synonym for 'hamming'. 17. ``Y = pdist(X, 'dice')`` Computes the Dice distance between each pair of boolean vectors. (see dice function documentation) 18. ``Y = pdist(X, 'kulczynski1')`` Computes the kulczynski1 distance between each pair of boolean vectors. (see kulczynski1 function documentation) 19. ``Y = pdist(X, 'rogerstanimoto')`` Computes the Rogers-Tanimoto distance between each pair of boolean vectors. (see rogerstanimoto function documentation) 20. ``Y = pdist(X, 'russellrao')`` Computes the Russell-Rao distance between each pair of boolean vectors. (see russellrao function documentation) 21. ``Y = pdist(X, 'sokalmichener')`` Computes the Sokal-Michener distance between each pair of boolean vectors. (see sokalmichener function documentation) 22. ``Y = pdist(X, 'sokalsneath')`` Computes the Sokal-Sneath distance between each pair of boolean vectors. (see sokalsneath function documentation) 23. ``Y = pdist(X, 'kulczynski1')`` Computes the Kulczynski 1 distance between each pair of boolean vectors. (see kulczynski1 function documentation) 24. ``Y = pdist(X, f)`` Computes the distance between all pairs of vectors in X using the user supplied 2-arity function f. For example, Euclidean distance between the vectors could be computed as follows:: dm = pdist(X, lambda u, v: np.sqrt(((u-v)**2).sum())) Note that you should avoid passing a reference to one of the distance functions defined in this library. For example,:: dm = pdist(X, sokalsneath) would calculate the pair-wise distances between the vectors in X using the Python function sokalsneath. This would result in sokalsneath being called :math:`{n \choose 2}` times, which is inefficient. Instead, the optimized C version is more efficient, and we call it using the following syntax.:: dm = pdist(X, 'sokalsneath') Examples -------- >>> import numpy as np >>> from scipy.spatial.distance import pdist ``x`` is an array of five points in three-dimensional space. >>> x = np.array([[2, 0, 2], [2, 2, 3], [-2, 4, 5], [0, 1, 9], [2, 2, 4]]) ``pdist(x)`` with no additional arguments computes the 10 pairwise Euclidean distances: >>> pdist(x) array([2.23606798, 6.40312424, 7.34846923, 2.82842712, 4.89897949, 6.40312424, 1. , 5.38516481, 4.58257569, 5.47722558]) The following computes the pairwise Minkowski distances with ``p = 3.5``: >>> pdist(x, metric='minkowski', p=3.5) array([2.04898923, 5.1154929 , 7.02700737, 2.43802731, 4.19042714, 6.03956994, 1. , 4.45128103, 4.10636143, 5.0619695 ]) The pairwise city block or Manhattan distances: >>> pdist(x, metric='cityblock') array([ 3., 11., 10., 4., 8., 9., 1., 9., 7., 8.]) rogerstanimoto(u, v, w=None) Compute the Rogers-Tanimoto dissimilarity between two boolean 1-D arrays. The Rogers-Tanimoto dissimilarity between two boolean 1-D arrays `u` and `v`, is defined as .. math:: \frac{R} {c_{TT} + c_{FF} + R} where :math:`c_{ij}` is the number of occurrences of :math:`\mathtt{u[k]} = i` and :math:`\mathtt{v[k]} = j` for :math:`k < n` and :math:`R = 2(c_{TF} + c_{FT})`. Parameters ---------- u : (N,) array_like, bool Input array. v : (N,) array_like, bool Input array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- rogerstanimoto : double The Rogers-Tanimoto dissimilarity between vectors `u` and `v`. Examples -------- >>> from scipy.spatial import distance >>> distance.rogerstanimoto([1, 0, 0], [0, 1, 0]) 0.8 >>> distance.rogerstanimoto([1, 0, 0], [1, 1, 0]) 0.5 >>> distance.rogerstanimoto([1, 0, 0], [2, 0, 0]) -1.0 russellrao(u, v, w=None) Compute the Russell-Rao dissimilarity between two boolean 1-D arrays. The Russell-Rao dissimilarity between two boolean 1-D arrays, `u` and `v`, is defined as .. math:: \frac{n - c_{TT}} {n} where :math:`c_{ij}` is the number of occurrences of :math:`\mathtt{u[k]} = i` and :math:`\mathtt{v[k]} = j` for :math:`k < n`. Parameters ---------- u : (N,) array_like, bool Input array. v : (N,) array_like, bool Input array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- russellrao : double The Russell-Rao dissimilarity between vectors `u` and `v`. Examples -------- >>> from scipy.spatial import distance >>> distance.russellrao([1, 0, 0], [0, 1, 0]) 1.0 >>> distance.russellrao([1, 0, 0], [1, 1, 0]) 0.6666666666666666 >>> distance.russellrao([1, 0, 0], [2, 0, 0]) 0.3333333333333333 seuclidean(u, v, V) Return the standardized Euclidean distance between two 1-D arrays. The standardized Euclidean distance between two n-vectors `u` and `v` is .. math:: \sqrt{\sum\limits_i \frac{1}{V_i} \left(u_i-v_i \right)^2} ``V`` is the variance vector; ``V[I]`` is the variance computed over all the i-th components of the points. If not passed, it is automatically computed. Parameters ---------- u : (N,) array_like Input array. v : (N,) array_like Input array. V : (N,) array_like `V` is an 1-D array of component variances. It is usually computed among a larger collection vectors. Returns ------- seuclidean : double The standardized Euclidean distance between vectors `u` and `v`. Examples -------- >>> from scipy.spatial import distance >>> distance.seuclidean([1, 0, 0], [0, 1, 0], [0.1, 0.1, 0.1]) 4.4721359549995796 >>> distance.seuclidean([1, 0, 0], [0, 1, 0], [1, 0.1, 0.1]) 3.3166247903553998 >>> distance.seuclidean([1, 0, 0], [0, 1, 0], [10, 0.1, 0.1]) 3.1780497164141406 sokalmichener(u, v, w=None) Compute the Sokal-Michener dissimilarity between two boolean 1-D arrays. The Sokal-Michener dissimilarity between boolean 1-D arrays `u` and `v`, is defined as .. math:: \frac{R} {S + R} where :math:`c_{ij}` is the number of occurrences of :math:`\mathtt{u[k]} = i` and :math:`\mathtt{v[k]} = j` for :math:`k < n`, :math:`R = 2 * (c_{TF} + c_{FT})` and :math:`S = c_{FF} + c_{TT}`. Parameters ---------- u : (N,) array_like, bool Input array. v : (N,) array_like, bool Input array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- sokalmichener : double The Sokal-Michener dissimilarity between vectors `u` and `v`. Examples -------- >>> from scipy.spatial import distance >>> distance.sokalmichener([1, 0, 0], [0, 1, 0]) 0.8 >>> distance.sokalmichener([1, 0, 0], [1, 1, 0]) 0.5 >>> distance.sokalmichener([1, 0, 0], [2, 0, 0]) -1.0 sokalsneath(u, v, w=None) Compute the Sokal-Sneath dissimilarity between two boolean 1-D arrays. The Sokal-Sneath dissimilarity between `u` and `v`, .. math:: \frac{R} {c_{TT} + R} where :math:`c_{ij}` is the number of occurrences of :math:`\mathtt{u[k]} = i` and :math:`\mathtt{v[k]} = j` for :math:`k < n` and :math:`R = 2(c_{TF} + c_{FT})`. Parameters ---------- u : (N,) array_like, bool Input array. v : (N,) array_like, bool Input array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- sokalsneath : double The Sokal-Sneath dissimilarity between vectors `u` and `v`. Examples -------- >>> from scipy.spatial import distance >>> distance.sokalsneath([1, 0, 0], [0, 1, 0]) 1.0 >>> distance.sokalsneath([1, 0, 0], [1, 1, 0]) 0.66666666666666663 >>> distance.sokalsneath([1, 0, 0], [2, 1, 0]) 0.0 >>> distance.sokalsneath([1, 0, 0], [3, 1, 0]) -2.0 sqeuclidean(u, v, w=None) Compute the squared Euclidean distance between two 1-D arrays. The squared Euclidean distance between `u` and `v` is defined as .. math:: \sum_i{w_i |u_i - v_i|^2} Parameters ---------- u : (N,) array_like Input array. v : (N,) array_like Input array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- sqeuclidean : double The squared Euclidean distance between vectors `u` and `v`. Examples -------- >>> from scipy.spatial import distance >>> distance.sqeuclidean([1, 0, 0], [0, 1, 0]) 2.0 >>> distance.sqeuclidean([1, 1, 0], [0, 1, 0]) 1.0 squareform(X, force='no', checks=True) Convert a vector-form distance vector to a square-form distance matrix, and vice-versa. Parameters ---------- X : array_like Either a condensed or redundant distance matrix. force : str, optional As with MATLAB(TM), if force is equal to ``'tovector'`` or ``'tomatrix'``, the input will be treated as a distance matrix or distance vector respectively. checks : bool, optional If set to False, no checks will be made for matrix symmetry nor zero diagonals. This is useful if it is known that ``X - X.T1`` is small and ``diag(X)`` is close to zero. These values are ignored any way so they do not disrupt the squareform transformation. Returns ------- Y : ndarray If a condensed distance matrix is passed, a redundant one is returned, or if a redundant one is passed, a condensed distance matrix is returned. Notes ----- 1. ``v = squareform(X)`` Given a square n-by-n symmetric distance matrix ``X``, ``v = squareform(X)`` returns a ``n * (n-1) / 2`` (i.e. binomial coefficient n choose 2) sized vector `v` where :math:`v[{n \choose 2} - {n-i \choose 2} + (j-i-1)]` is the distance between distinct points ``i`` and ``j``. If ``X`` is non-square or asymmetric, an error is raised. 2. ``X = squareform(v)`` Given a ``n * (n-1) / 2`` sized vector ``v`` for some integer ``n >= 1`` encoding distances as described, ``X = squareform(v)`` returns a n-by-n distance matrix ``X``. The ``X[i, j]`` and ``X[j, i]`` values are set to :math:`v[{n \choose 2} - {n-i \choose 2} + (j-i-1)]` and all diagonal elements are zero. In SciPy 0.19.0, ``squareform`` stopped casting all input types to float64, and started returning arrays of the same dtype as the input. Examples -------- >>> import numpy as np >>> from scipy.spatial.distance import pdist, squareform ``x`` is an array of five points in three-dimensional space. >>> x = np.array([[2, 0, 2], [2, 2, 3], [-2, 4, 5], [0, 1, 9], [2, 2, 4]]) ``pdist(x)`` computes the Euclidean distances between each pair of points in ``x``. The distances are returned in a one-dimensional array with length ``5*(5 - 1)/2 = 10``. >>> distvec = pdist(x) >>> distvec array([2.23606798, 6.40312424, 7.34846923, 2.82842712, 4.89897949, 6.40312424, 1. , 5.38516481, 4.58257569, 5.47722558]) ``squareform(distvec)`` returns the 5x5 distance matrix. >>> m = squareform(distvec) >>> m array([[0. , 2.23606798, 6.40312424, 7.34846923, 2.82842712], [2.23606798, 0. , 4.89897949, 6.40312424, 1. ], [6.40312424, 4.89897949, 0. , 5.38516481, 4.58257569], [7.34846923, 6.40312424, 5.38516481, 0. , 5.47722558], [2.82842712, 1. , 4.58257569, 5.47722558, 0. ]]) When given a square distance matrix ``m``, ``squareform(m)`` returns the one-dimensional condensed distance vector associated with the matrix. In this case, we recover ``distvec``. >>> squareform(m) array([2.23606798, 6.40312424, 7.34846923, 2.82842712, 4.89897949, 6.40312424, 1. , 5.38516481, 4.58257569, 5.47722558]) yule(u, v, w=None) Compute the Yule dissimilarity between two boolean 1-D arrays. The Yule dissimilarity is defined as .. math:: \frac{R}{c_{TT} * c_{FF} + \frac{R}{2}} where :math:`c_{ij}` is the number of occurrences of :math:`\mathtt{u[k]} = i` and :math:`\mathtt{v[k]} = j` for :math:`k < n` and :math:`R = 2.0 * c_{TF} * c_{FT}`. Parameters ---------- u : (N,) array_like, bool Input array. v : (N,) array_like, bool Input array. w : (N,) array_like, optional The weights for each value in `u` and `v`. Default is None, which gives each value a weight of 1.0 Returns ------- yule : double The Yule dissimilarity between vectors `u` and `v`. Examples -------- >>> from scipy.spatial import distance >>> distance.yule([1, 0, 0], [0, 1, 0]) 2.0 >>> distance.yule([1, 1, 0], [0, 1, 0]) 0.0 DATA __all__ = ['braycurtis', 'canberra', 'cdist', 'chebyshev', 'cityblock'... FILE c:\users\mertg\anaconda3\lib\site-packages\scipy\spatial\distance.py
In k-means clustering we are given a set of $d$-dimensional vectors and we want to identify k sets $S_i$ such that
$$\sum_{i=0}^k \sum_{x_j \in S_i} ||x_j - \mu_i||^2$$is minimized where $\mu_i$ is the mean of cluster $S_i$. That is, all points are close as possible to the 'center' of the cluster.
Limitations
General algorithm
Will converge to local optimum.
First let's make a toy data set...
import scipy.cluster.vq as vq #vq: vector quantization
import numpy as np
import matplotlib.pylab as plt
%matplotlib inline
randpts1 = np.random.randn(100,2)/(4,1) #100 integer coordinates in the range [0:50],[0:50]
randpts2 = (np.random.randn(100,2)+(1,0))/(1,4)
plt.plot(randpts1[:,0],randpts1[:,1],'o',randpts2[:,0],randpts2[:,1],'o')
randpts = np.vstack((randpts1,randpts2))
(means,clusters) = vq.kmeans2(randpts,2)#returns tuple of means and cluster assignments
The means are the cluster centers
plt.scatter(randpts[:,0],randpts[:,1],c=clusters)
plt.plot(means[:,0],means[:,1],'*',ms=20,c='red');
(means,clusters) = vq.kmeans2(randpts,3)
plt.scatter(randpts[:,0],randpts[:,1],c=clusters)
plt.plot(means[:,0],means[:,1],'*',ms=20,c='red');
(means,clusters) = vq.kmeans2(randpts,4)
plt.scatter(randpts[:,0],randpts[:,1],c=clusters)
plt.plot(means[:,0],means[:,1],'*',ms=20,c='red');
%%html
<div id="kmean" style="width: 500px"></div>
<script>
$('head').append('<link rel="stylesheet" href="https://bits.csb.pitt.edu/asker.js/themes/asker.default.css" />');
var divid = '#kmean';
jQuery(divid).asker({
id: divid,
question: "Will k-means always find the same set of clusters?",
answers: ['Yes','No','Depends'],
server: "https://bits.csb.pitt.edu/asker.js/example/asker.cgi",
charter: chartmaker})
$(".jp-InputArea .o:contains(html)").closest('.jp-InputArea').hide();
</script>
Vector quantization is just a fancy way to describe assigning clusters to new points.
newrand = np.random.randn(100,2)
code,dist = vq.vq(newrand,means)
plt.scatter(newrand[:,0],newrand[:,1],c=code)
plt.plot(means[:,0],means[:,1],'*',ms=20);
%%html
<div id="clus1" style="width: 500px"></div>
<script>
$('head').append('<link rel="stylesheet" href="https://bits.csb.pitt.edu/asker.js/themes/asker.default.css" />');
var divid = '#clus1';
jQuery(divid).asker({
id: divid,
question: "What sort of data would k-means have difficulty clustering?",
answers: ['Expression data','Dose-response data','Protein structures','Sequences'],
server: "https://bits.csb.pitt.edu/asker.js/example/asker.cgi",
charter: chartmaker})
$(".jp-InputArea .o:contains(html)").closest('.jp-InputArea').hide();
</script>
Hierarchical clustering creates a heirarchy, where each cluster is formed from subclusters.
Agglomerative builds this hierarchy from the bottom up: start with all singleton clusters, find the two clusters that are closest, combine them into a cluster, repeat.
This requires there be a notion of distance between clusters of items, not just the items themselves.
Important: All you need is a distance function - you do not need to be able to take an average (as with k-means).
%%html
<img src="imgs/clusterpoints.png">
<div id="cluspts" style="width: 500px"></div>
<script>
$('head').append('<link rel="stylesheet" href="https://bits.csb.pitt.edu/asker.js/themes/asker.default.css" />');
var divid = '#cluspts';
jQuery(divid).asker({
id: divid,
question: "What cluster is closest to red by single linkage? complete?",
answers: ['blue, blue','blue, yellow','yellow, blue','yellow, yellow'],
server: "https://bits.csb.pitt.edu/asker.js/example/asker.cgi",
charter: chartmaker})
$(".jp-InputArea .o:contains(html)").closest('.jp-InputArea').hide();
</script>
linkage
¶scipy.cluster.hierarchy.linkage
creates a clustering hierarchy. It takes three parameters:
import scipy.cluster.hierarchy as hclust
linkage_matrix = hclust.linkage(randpts)
A (n−1) by 4 matrix Z is returned. At the i-th iteration, clusters with indices Z[i, 0] and Z[i, 1] are combined to form cluster n+i. A cluster with an index less than n corresponds to one of the n original observations. The distance between clusters Z[i, 0] and Z[i, 1] is given by Z[i, 2]. The fourth value Z[i, 3] represents the number of original observations in the newly formed cluster.
linkage_matrix.shape
(199, 4)
linkage_matrix
array([[1.49000000e+02, 1.71000000e+02, 4.46097932e-03, 2.00000000e+00], [4.60000000e+01, 7.20000000e+01, 6.85261819e-03, 2.00000000e+00], [1.60000000e+01, 7.30000000e+01, 1.51521318e-02, 2.00000000e+00], [1.37000000e+02, 1.57000000e+02, 1.53148351e-02, 2.00000000e+00], [1.19000000e+02, 1.89000000e+02, 1.78213509e-02, 2.00000000e+00], [1.22000000e+02, 1.98000000e+02, 2.04763202e-02, 2.00000000e+00], [1.34000000e+02, 2.00000000e+02, 2.35915430e-02, 3.00000000e+00], [1.38000000e+02, 1.87000000e+02, 2.65878878e-02, 2.00000000e+00], [2.40000000e+01, 6.90000000e+01, 2.93336673e-02, 2.00000000e+00], [6.00000000e+01, 9.60000000e+01, 2.99804179e-02, 2.00000000e+00], [1.82000000e+02, 1.85000000e+02, 3.14543289e-02, 2.00000000e+00], [1.54000000e+02, 1.96000000e+02, 3.38672911e-02, 2.00000000e+00], [9.00000000e+00, 1.76000000e+02, 3.54702089e-02, 2.00000000e+00], [3.90000000e+01, 2.12000000e+02, 3.56342391e-02, 3.00000000e+00], [2.03000000e+02, 2.09000000e+02, 3.78817319e-02, 4.00000000e+00], [1.15000000e+02, 1.47000000e+02, 4.09620150e-02, 2.00000000e+00], [3.00000000e+00, 1.74000000e+02, 4.09881290e-02, 2.00000000e+00], [6.00000000e+00, 9.90000000e+01, 4.14929659e-02, 2.00000000e+00], [9.00000000e+01, 1.72000000e+02, 4.16513026e-02, 2.00000000e+00], [1.40000000e+01, 7.60000000e+01, 4.26578945e-02, 2.00000000e+00], [1.30000000e+01, 4.10000000e+01, 4.30331868e-02, 2.00000000e+00], [1.27000000e+02, 2.15000000e+02, 4.37628602e-02, 3.00000000e+00], [1.36000000e+02, 1.64000000e+02, 4.38642461e-02, 2.00000000e+00], [6.20000000e+01, 2.13000000e+02, 4.46924715e-02, 4.00000000e+00], [1.68000000e+02, 1.91000000e+02, 4.64564965e-02, 2.00000000e+00], [1.35000000e+02, 1.41000000e+02, 4.71929887e-02, 2.00000000e+00], [8.70000000e+01, 2.16000000e+02, 4.78129247e-02, 3.00000000e+00], [1.53000000e+02, 2.02000000e+02, 4.80458906e-02, 3.00000000e+00], [5.80000000e+01, 7.50000000e+01, 4.90392524e-02, 2.00000000e+00], [2.00000000e+01, 2.26000000e+02, 5.04661397e-02, 4.00000000e+00], [2.00000000e+00, 2.29000000e+02, 5.12219112e-02, 5.00000000e+00], [2.70000000e+01, 1.56000000e+02, 5.27747011e-02, 2.00000000e+00], [4.00000000e+00, 2.01000000e+02, 5.40595777e-02, 3.00000000e+00], [3.10000000e+01, 5.50000000e+01, 5.53762069e-02, 2.00000000e+00], [8.00000000e+00, 1.94000000e+02, 5.62458425e-02, 2.00000000e+00], [5.00000000e+01, 1.88000000e+02, 5.65509970e-02, 2.00000000e+00], [1.50000000e+01, 2.30000000e+02, 5.71721638e-02, 6.00000000e+00], [2.14000000e+02, 2.28000000e+02, 5.76827887e-02, 6.00000000e+00], [4.70000000e+01, 5.20000000e+01, 5.78110419e-02, 2.00000000e+00], [3.50000000e+01, 9.40000000e+01, 5.82658131e-02, 2.00000000e+00], [2.32000000e+02, 2.39000000e+02, 5.86789916e-02, 5.00000000e+00], [1.62000000e+02, 1.83000000e+02, 5.86848206e-02, 2.00000000e+00], [1.70000000e+02, 1.77000000e+02, 5.86978283e-02, 2.00000000e+00], [1.80000000e+01, 2.17000000e+02, 5.91950496e-02, 3.00000000e+00], [8.20000000e+01, 2.19000000e+02, 6.11521167e-02, 3.00000000e+00], [3.70000000e+01, 2.23000000e+02, 6.12666247e-02, 5.00000000e+00], [4.80000000e+01, 5.90000000e+01, 6.28201204e-02, 2.00000000e+00], [1.07000000e+02, 2.10000000e+02, 6.35916605e-02, 3.00000000e+00], [3.40000000e+01, 2.27000000e+02, 6.37643821e-02, 4.00000000e+00], [1.25000000e+02, 1.84000000e+02, 6.38771083e-02, 2.00000000e+00], [1.20000000e+02, 2.34000000e+02, 6.75200732e-02, 3.00000000e+00], [5.10000000e+01, 2.38000000e+02, 6.75869041e-02, 3.00000000e+00], [1.29000000e+02, 2.42000000e+02, 6.80689763e-02, 3.00000000e+00], [2.80000000e+01, 3.30000000e+01, 6.84683645e-02, 2.00000000e+00], [6.30000000e+01, 2.44000000e+02, 6.84799076e-02, 4.00000000e+00], [7.10000000e+01, 2.45000000e+02, 7.08571666e-02, 6.00000000e+00], [1.03000000e+02, 1.23000000e+02, 7.10883173e-02, 2.00000000e+00], [2.48000000e+02, 2.55000000e+02, 7.16967897e-02, 1.00000000e+01], [2.20000000e+01, 1.00000000e+02, 7.24315337e-02, 2.00000000e+00], [1.16000000e+02, 2.04000000e+02, 7.24882884e-02, 3.00000000e+00], [1.55000000e+02, 2.50000000e+02, 7.27899910e-02, 4.00000000e+00], [1.30000000e+02, 1.31000000e+02, 7.44755175e-02, 2.00000000e+00], [2.11000000e+02, 2.41000000e+02, 7.49720297e-02, 4.00000000e+00], [8.00000000e+01, 2.57000000e+02, 7.53968749e-02, 1.10000000e+01], [1.92000000e+02, 2.24000000e+02, 7.75842496e-02, 3.00000000e+00], [1.26000000e+02, 1.51000000e+02, 7.84050402e-02, 2.00000000e+00], [5.70000000e+01, 2.40000000e+02, 7.84796537e-02, 6.00000000e+00], [2.58000000e+02, 2.60000000e+02, 7.89227377e-02, 6.00000000e+00], [1.66000000e+02, 1.79000000e+02, 7.94677176e-02, 2.00000000e+00], [2.54000000e+02, 2.63000000e+02, 8.15415392e-02, 1.50000000e+01], [5.60000000e+01, 6.50000000e+01, 8.20849532e-02, 2.00000000e+00], [2.52000000e+02, 2.56000000e+02, 8.33896565e-02, 5.00000000e+00], [1.80000000e+02, 2.25000000e+02, 8.43081124e-02, 3.00000000e+00], [2.33000000e+02, 2.37000000e+02, 8.44501404e-02, 8.00000000e+00], [2.49000000e+02, 2.64000000e+02, 8.50561984e-02, 5.00000000e+00], [7.00000000e+01, 2.73000000e+02, 8.54845459e-02, 9.00000000e+00], [1.14000000e+02, 2.65000000e+02, 8.63919637e-02, 3.00000000e+00], [2.05000000e+02, 2.67000000e+02, 8.65156493e-02, 8.00000000e+00], [1.90000000e+01, 1.95000000e+02, 8.88527318e-02, 2.00000000e+00], [1.46000000e+02, 2.68000000e+02, 8.90563045e-02, 3.00000000e+00], [8.50000000e+01, 9.70000000e+01, 8.93399421e-02, 2.00000000e+00], [0.00000000e+00, 2.90000000e+01, 9.00439497e-02, 2.00000000e+00], [1.69000000e+02, 2.76000000e+02, 9.04181689e-02, 4.00000000e+00], [2.61000000e+02, 2.69000000e+02, 9.15308412e-02, 1.70000000e+01], [1.81000000e+02, 2.71000000e+02, 9.24404679e-02, 6.00000000e+00], [1.10000000e+02, 2.62000000e+02, 9.24512863e-02, 5.00000000e+00], [2.06000000e+02, 2.59000000e+02, 9.28490269e-02, 6.00000000e+00], [2.21000000e+02, 2.85000000e+02, 9.33121189e-02, 8.00000000e+00], [2.10000000e+01, 2.80000000e+02, 9.33449228e-02, 3.00000000e+00], [2.46000000e+02, 2.75000000e+02, 9.44668630e-02, 1.10000000e+01], [9.20000000e+01, 2.81000000e+02, 9.82526818e-02, 3.00000000e+00], [3.20000000e+01, 8.90000000e+01, 9.83514763e-02, 2.00000000e+00], [2.66000000e+02, 2.78000000e+02, 9.92969524e-02, 8.00000000e+00], [1.70000000e+01, 2.83000000e+02, 1.00235834e-01, 1.80000000e+01], [2.50000000e+01, 9.50000000e+01, 1.01665792e-01, 2.00000000e+00], [1.86000000e+02, 2.36000000e+02, 1.07180172e-01, 7.00000000e+00], [9.80000000e+01, 2.90000000e+02, 1.07841537e-01, 4.00000000e+00], [4.00000000e+01, 6.10000000e+01, 1.08468612e-01, 2.00000000e+00], [2.74000000e+02, 2.82000000e+02, 1.09930262e-01, 9.00000000e+00], [1.04000000e+02, 1.99000000e+02, 1.10531529e-01, 2.00000000e+00], [2.77000000e+02, 2.98000000e+02, 1.13211503e-01, 1.70000000e+01], [2.07000000e+02, 3.00000000e+02, 1.13522406e-01, 1.90000000e+01], [8.30000000e+01, 3.01000000e+02, 1.14183848e-01, 2.00000000e+01], [1.00000000e+00, 1.18000000e+02, 1.15628703e-01, 2.00000000e+00], [1.33000000e+02, 1.59000000e+02, 1.15690794e-01, 2.00000000e+00], [2.88000000e+02, 2.96000000e+02, 1.16741096e-01, 7.00000000e+00], [5.40000000e+01, 2.35000000e+02, 1.18258150e-01, 3.00000000e+00], [7.70000000e+01, 9.10000000e+01, 1.18371150e-01, 2.00000000e+00], [3.00000000e+01, 2.20000000e+02, 1.18453723e-01, 3.00000000e+00], [1.11000000e+02, 1.63000000e+02, 1.18467821e-01, 2.00000000e+00], [1.08000000e+02, 1.58000000e+02, 1.18605371e-01, 2.00000000e+00], [2.89000000e+02, 3.06000000e+02, 1.20369073e-01, 1.40000000e+01], [1.12000000e+02, 2.84000000e+02, 1.20939623e-01, 7.00000000e+00], [2.31000000e+02, 2.95000000e+02, 1.21421162e-01, 9.00000000e+00], [2.92000000e+02, 3.11000000e+02, 1.21908215e-01, 2.20000000e+01], [2.30000000e+01, 3.60000000e+01, 1.24742435e-01, 2.00000000e+00], [1.00000000e+01, 7.40000000e+01, 1.25836946e-01, 2.00000000e+00], [2.93000000e+02, 3.14000000e+02, 1.27005757e-01, 4.00000000e+01], [1.40000000e+02, 3.17000000e+02, 1.27480221e-01, 4.10000000e+01], [1.61000000e+02, 2.79000000e+02, 1.28443916e-01, 4.00000000e+00], [2.18000000e+02, 3.18000000e+02, 1.30309737e-01, 4.30000000e+01], [3.13000000e+02, 3.20000000e+02, 1.30499868e-01, 5.20000000e+01], [3.05000000e+02, 3.21000000e+02, 1.31250675e-01, 5.90000000e+01], [3.07000000e+02, 3.15000000e+02, 1.32289231e-01, 4.00000000e+00], [2.43000000e+02, 2.94000000e+02, 1.32325830e-01, 5.00000000e+00], [3.09000000e+02, 3.12000000e+02, 1.32484499e-01, 9.00000000e+00], [3.03000000e+02, 3.22000000e+02, 1.33829293e-01, 6.10000000e+01], [1.67000000e+02, 2.22000000e+02, 1.34803524e-01, 3.00000000e+00], [1.02000000e+02, 3.04000000e+02, 1.36009814e-01, 3.00000000e+00], [1.13000000e+02, 1.78000000e+02, 1.37101208e-01, 2.00000000e+00], [4.40000000e+01, 8.10000000e+01, 1.37338461e-01, 2.00000000e+00], [7.90000000e+01, 3.08000000e+02, 1.37668275e-01, 4.00000000e+00], [1.24000000e+02, 3.19000000e+02, 1.38750896e-01, 5.00000000e+00], [3.02000000e+02, 3.26000000e+02, 1.40738695e-01, 8.10000000e+01], [2.08000000e+02, 2.53000000e+02, 1.40804349e-01, 4.00000000e+00], [3.80000000e+01, 3.33000000e+02, 1.41390485e-01, 8.20000000e+01], [4.90000000e+01, 3.31000000e+02, 1.42777393e-01, 5.00000000e+00], [3.25000000e+02, 3.32000000e+02, 1.42966246e-01, 1.40000000e+01], [1.10000000e+01, 3.30000000e+02, 1.43558272e-01, 3.00000000e+00], [8.40000000e+01, 3.35000000e+02, 1.49205129e-01, 8.30000000e+01], [1.21000000e+02, 3.39000000e+02, 1.50857936e-01, 8.40000000e+01], [2.87000000e+02, 3.40000000e+02, 1.53037165e-01, 9.20000000e+01], [2.60000000e+01, 3.41000000e+02, 1.53058594e-01, 9.30000000e+01], [6.40000000e+01, 3.42000000e+02, 1.53485686e-01, 9.40000000e+01], [2.51000000e+02, 3.34000000e+02, 1.55617162e-01, 7.00000000e+00], [1.93000000e+02, 3.43000000e+02, 1.55680672e-01, 9.50000000e+01], [1.60000000e+02, 3.45000000e+02, 1.57148964e-01, 9.60000000e+01], [3.24000000e+02, 3.46000000e+02, 1.57829263e-01, 1.01000000e+02], [4.20000000e+01, 3.16000000e+02, 1.59739095e-01, 3.00000000e+00], [3.27000000e+02, 3.29000000e+02, 1.62354589e-01, 5.00000000e+00], [3.37000000e+02, 3.49000000e+02, 1.62365869e-01, 1.90000000e+01], [1.52000000e+02, 1.65000000e+02, 1.62771714e-01, 2.00000000e+00], [1.06000000e+02, 3.50000000e+02, 1.64820991e-01, 2.00000000e+01], [3.28000000e+02, 3.47000000e+02, 1.66258090e-01, 1.04000000e+02], [3.23000000e+02, 3.53000000e+02, 1.66872701e-01, 1.08000000e+02], [3.44000000e+02, 3.54000000e+02, 1.67675789e-01, 1.15000000e+02], [2.72000000e+02, 2.91000000e+02, 1.70312886e-01, 5.00000000e+00], [1.05000000e+02, 3.51000000e+02, 1.70622544e-01, 3.00000000e+00], [1.17000000e+02, 1.44000000e+02, 1.73703505e-01, 2.00000000e+00], [1.43000000e+02, 3.52000000e+02, 1.74719291e-01, 2.10000000e+01], [7.00000000e+00, 3.55000000e+02, 1.75831645e-01, 1.16000000e+02], [1.28000000e+02, 3.60000000e+02, 1.80161169e-01, 1.17000000e+02], [3.48000000e+02, 3.61000000e+02, 1.82127024e-01, 1.20000000e+02], [1.48000000e+02, 2.99000000e+02, 1.86143420e-01, 3.00000000e+00], [3.56000000e+02, 3.62000000e+02, 1.89421685e-01, 1.25000000e+02], [2.70000000e+02, 3.64000000e+02, 1.96936021e-01, 1.27000000e+02], [1.75000000e+02, 3.59000000e+02, 1.96974837e-01, 2.20000000e+01], [1.20000000e+01, 4.30000000e+01, 1.97920845e-01, 2.00000000e+00], [2.97000000e+02, 3.36000000e+02, 2.00391424e-01, 7.00000000e+00], [1.39000000e+02, 3.65000000e+02, 2.01299338e-01, 1.28000000e+02], [6.70000000e+01, 3.67000000e+02, 2.04332642e-01, 3.00000000e+00], [2.86000000e+02, 3.66000000e+02, 2.12902916e-01, 2.80000000e+01], [3.69000000e+02, 3.71000000e+02, 2.13142279e-01, 1.56000000e+02], [1.32000000e+02, 3.72000000e+02, 2.18065620e-01, 1.57000000e+02], [1.42000000e+02, 3.73000000e+02, 2.18451186e-01, 1.58000000e+02], [3.58000000e+02, 3.74000000e+02, 2.18791278e-01, 1.60000000e+02], [3.57000000e+02, 3.75000000e+02, 2.21760753e-01, 1.63000000e+02], [1.01000000e+02, 3.76000000e+02, 2.35723986e-01, 1.64000000e+02], [3.63000000e+02, 3.77000000e+02, 2.43024267e-01, 1.67000000e+02], [5.00000000e+00, 3.68000000e+02, 2.44111723e-01, 8.00000000e+00], [1.90000000e+02, 3.78000000e+02, 2.44400296e-01, 1.68000000e+02], [2.47000000e+02, 3.80000000e+02, 2.46223922e-01, 1.71000000e+02], [5.30000000e+01, 3.79000000e+02, 2.50725745e-01, 9.00000000e+00], [1.97000000e+02, 3.81000000e+02, 2.54748265e-01, 1.72000000e+02], [7.80000000e+01, 3.83000000e+02, 2.55507470e-01, 1.73000000e+02], [3.38000000e+02, 3.84000000e+02, 2.61522515e-01, 1.76000000e+02], [3.70000000e+02, 3.82000000e+02, 3.00532955e-01, 1.20000000e+01], [3.10000000e+02, 3.85000000e+02, 3.14559328e-01, 1.78000000e+02], [4.50000000e+01, 3.87000000e+02, 3.26139012e-01, 1.79000000e+02], [6.80000000e+01, 3.88000000e+02, 3.95954374e-01, 1.80000000e+02], [3.86000000e+02, 3.89000000e+02, 3.98516147e-01, 1.92000000e+02], [1.73000000e+02, 3.90000000e+02, 4.15355443e-01, 1.93000000e+02], [1.09000000e+02, 1.50000000e+02, 4.41810997e-01, 2.00000000e+00], [6.60000000e+01, 3.91000000e+02, 5.56731638e-01, 1.94000000e+02], [1.45000000e+02, 3.92000000e+02, 7.08316589e-01, 3.00000000e+00], [3.93000000e+02, 3.94000000e+02, 7.69909958e-01, 1.97000000e+02], [8.80000000e+01, 9.30000000e+01, 8.46319094e-01, 2.00000000e+00], [8.60000000e+01, 3.95000000e+02, 8.79918242e-01, 1.98000000e+02], [3.96000000e+02, 3.97000000e+02, 9.84658940e-01, 2.00000000e+02]])
hclust.dendrogram(linkage_matrix,p=10,truncate_mode='level',no_labels=True);#show first 10 levels
The cophenetic distance between two observations that have been clustered is defined to be the intergroup dissimilarity at which the two observations are first combined into a single cluster. It is shown as the height of the U-links.
fcluster
: extracting clusters from a hierarchy¶fcluster
takes a linkage matrix and returns a cluster assignment. It takes a threshold value and a string specifying what method to use to form the cluster.
help(hclust.fcluster)
Help on function fcluster in module scipy.cluster.hierarchy: fcluster(Z, t, criterion='inconsistent', depth=2, R=None, monocrit=None) Form flat clusters from the hierarchical clustering defined by the given linkage matrix. Parameters ---------- Z : ndarray The hierarchical clustering encoded with the matrix returned by the `linkage` function. t : scalar For criteria 'inconsistent', 'distance' or 'monocrit', this is the threshold to apply when forming flat clusters. For 'maxclust' or 'maxclust_monocrit' criteria, this would be max number of clusters requested. criterion : str, optional The criterion to use in forming flat clusters. This can be any of the following values: ``inconsistent`` : If a cluster node and all its descendants have an inconsistent value less than or equal to `t`, then all its leaf descendants belong to the same flat cluster. When no non-singleton cluster meets this criterion, every node is assigned to its own cluster. (Default) ``distance`` : Forms flat clusters so that the original observations in each flat cluster have no greater a cophenetic distance than `t`. ``maxclust`` : Finds a minimum threshold ``r`` so that the cophenetic distance between any two original observations in the same flat cluster is no more than ``r`` and no more than `t` flat clusters are formed. ``monocrit`` : Forms a flat cluster from a cluster node c with index i when ``monocrit[j] <= t``. For example, to threshold on the maximum mean distance as computed in the inconsistency matrix R with a threshold of 0.8 do:: MR = maxRstat(Z, R, 3) fcluster(Z, t=0.8, criterion='monocrit', monocrit=MR) ``maxclust_monocrit`` : Forms a flat cluster from a non-singleton cluster node ``c`` when ``monocrit[i] <= r`` for all cluster indices ``i`` below and including ``c``. ``r`` is minimized such that no more than ``t`` flat clusters are formed. monocrit must be monotonic. For example, to minimize the threshold t on maximum inconsistency values so that no more than 3 flat clusters are formed, do:: MI = maxinconsts(Z, R) fcluster(Z, t=3, criterion='maxclust_monocrit', monocrit=MI) depth : int, optional The maximum depth to perform the inconsistency calculation. It has no meaning for the other criteria. Default is 2. R : ndarray, optional The inconsistency matrix to use for the 'inconsistent' criterion. This matrix is computed if not provided. monocrit : ndarray, optional An array of length n-1. `monocrit[i]` is the statistics upon which non-singleton i is thresholded. The monocrit vector must be monotonic, i.e., given a node c with index i, for all node indices j corresponding to nodes below c, ``monocrit[i] >= monocrit[j]``. Returns ------- fcluster : ndarray An array of length ``n``. ``T[i]`` is the flat cluster number to which original observation ``i`` belongs. See Also -------- linkage : for information about hierarchical clustering methods work. Examples -------- >>> from scipy.cluster.hierarchy import ward, fcluster >>> from scipy.spatial.distance import pdist All cluster linkage methods - e.g., `scipy.cluster.hierarchy.ward` generate a linkage matrix ``Z`` as their output: >>> X = [[0, 0], [0, 1], [1, 0], ... [0, 4], [0, 3], [1, 4], ... [4, 0], [3, 0], [4, 1], ... [4, 4], [3, 4], [4, 3]] >>> Z = ward(pdist(X)) >>> Z array([[ 0. , 1. , 1. , 2. ], [ 3. , 4. , 1. , 2. ], [ 6. , 7. , 1. , 2. ], [ 9. , 10. , 1. , 2. ], [ 2. , 12. , 1.29099445, 3. ], [ 5. , 13. , 1.29099445, 3. ], [ 8. , 14. , 1.29099445, 3. ], [11. , 15. , 1.29099445, 3. ], [16. , 17. , 5.77350269, 6. ], [18. , 19. , 5.77350269, 6. ], [20. , 21. , 8.16496581, 12. ]]) This matrix represents a dendrogram, where the first and second elements are the two clusters merged at each step, the third element is the distance between these clusters, and the fourth element is the size of the new cluster - the number of original data points included. `scipy.cluster.hierarchy.fcluster` can be used to flatten the dendrogram, obtaining as a result an assignation of the original data points to single clusters. This assignation mostly depends on a distance threshold ``t`` - the maximum inter-cluster distance allowed: >>> fcluster(Z, t=0.9, criterion='distance') array([ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12], dtype=int32) >>> fcluster(Z, t=1.1, criterion='distance') array([1, 1, 2, 3, 3, 4, 5, 5, 6, 7, 7, 8], dtype=int32) >>> fcluster(Z, t=3, criterion='distance') array([1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4], dtype=int32) >>> fcluster(Z, t=9, criterion='distance') array([1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1], dtype=int32) In the first case, the threshold ``t`` is too small to allow any two samples in the data to form a cluster, so 12 different clusters are returned. In the second case, the threshold is large enough to allow the first 4 points to be merged with their nearest neighbors. So, here, only 8 clusters are returned. The third case, with a much higher threshold, allows for up to 8 data points to be connected - so 4 clusters are returned here. Lastly, the threshold of the fourth case is large enough to allow for all data points to be merged together - so a single cluster is returned.
clusters = hclust.fcluster(linkage_matrix,0.3,'distance')
len(set(clusters))
14
plt.scatter(randpts[:,0],randpts[:,1],c=clusters);
clusters = hclust.fcluster(linkage_matrix,4,'maxclust')
len(set(clusters))
4
plt.scatter(randpts[:,0],randpts[:,1],c=clusters)
<matplotlib.collections.PathCollection at 0x135996b4550>
fclusterdata
¶fclusterdata
does both linkage and fcluster in one step. Let's try out different linkage methods.
clusters = hclust.fclusterdata(randpts,.3,criterion='distance',method='single')
plt.scatter(randpts[:,0],randpts[:,1],c=clusters)
len(set(clusters))
14
clusters = hclust.fclusterdata(randpts,.3,criterion='distance',method='complete')
plt.scatter(randpts[:,0],randpts[:,1],c=clusters);
len(set(clusters))
63
clusters = hclust.fclusterdata(randpts,4,'maxclust',method='complete')
plt.scatter(randpts[:,0],randpts[:,1],c=clusters);
clusters = hclust.fclusterdata(randpts,4,'maxclust',method='average')
plt.scatter(randpts[:,0],randpts[:,1],c=clusters);
You can even use a non-Euclidean metric.
clusters = hclust.fclusterdata(randpts,4,'maxclust',method='complete',metric='cityblock')
plt.scatter(randpts[:,0],randpts[:,1],c=clusters);
import sklearn
import sklearn.datasets
roll,_=sklearn.datasets.make_swiss_roll()
roll = roll[:,[0,2]]
clusters=hclust.fclusterdata(roll,5,'maxclust',method='single')
plt.scatter(roll[:,0],roll[:,1],c=clusters)
plt.savefig('imgs/roll.png',bbox_inches='tight')
%%html
<img src="imgs/roll.png">
<div id="clusroll" style="width: 500px"></div>
<script>
$('head').append('<link rel="stylesheet" href="https://bits.csb.pitt.edu/asker.js/themes/asker.default.css" />');
var divid = '#clusroll';
jQuery(divid).asker({
id: divid,
question: "What linkage was likely used to form these clusters?",
answers: ['average','complete','single'],
server: "https://bits.csb.pitt.edu/asker.js/example/asker.cgi",
charter: chartmaker})
$(".jp-InputArea .o:contains(html)").closest('.jp-InputArea').hide();
</script>
leaves_list
¶A hierarchical cluster imposes an order on the leaves. You can retrieve this ordering from the linkage matrix with leaves_list
hclust.leaves_list(linkage_matrix)
array([ 88, 93, 86, 66, 173, 67, 12, 43, 53, 5, 40, 61, 49, 79, 30, 13, 41, 68, 45, 108, 158, 11, 44, 81, 78, 197, 107, 182, 185, 190, 148, 104, 199, 101, 105, 152, 165, 117, 144, 142, 132, 139, 56, 65, 180, 135, 141, 32, 89, 42, 10, 74, 128, 7, 51, 47, 52, 24, 69, 28, 33, 77, 91, 23, 36, 102, 133, 159, 18, 6, 99, 25, 95, 160, 193, 64, 26, 127, 115, 147, 110, 154, 196, 162, 183, 121, 84, 38, 83, 138, 187, 122, 198, 22, 100, 155, 120, 8, 194, 125, 184, 192, 168, 191, 169, 114, 126, 151, 1, 118, 21, 85, 97, 98, 92, 0, 29, 27, 156, 186, 15, 2, 20, 87, 3, 174, 90, 172, 140, 17, 130, 131, 63, 82, 14, 76, 80, 34, 153, 16, 73, 71, 37, 62, 39, 9, 176, 57, 4, 46, 72, 35, 94, 19, 195, 48, 59, 70, 31, 55, 137, 157, 60, 96, 58, 75, 54, 50, 188, 134, 149, 171, 116, 119, 189, 175, 143, 106, 111, 163, 112, 181, 129, 170, 177, 103, 123, 124, 161, 146, 166, 179, 167, 136, 164, 113, 178, 145, 109, 150], dtype=int32)
plt.figure(figsize=(16,3))
hclust.dendrogram(linkage_matrix);
%%html
<div id="listorder" style="width: 500px"></div>
<script>
$('head').append('<link rel="stylesheet" href="https://bits.csb.pitt.edu/asker.js/themes/asker.default.css" />');
var divid = '#listorder';
jQuery(divid).asker({
id: divid,
question: "Is this order unique for a given linkage matrix?",
answers: ['Yes','No'],
server: "https://bits.csb.pitt.edu/asker.js/example/asker.cgi",
charter: chartmaker})
$(".jp-InputArea .o:contains(html)").closest('.jp-InputArea').hide();
</script>
np.genfromtxt
)plt.matshow
)!wget https://asinansaglam.github.io/python_bio_2022/files/Spellman.csv
--2023-10-16 16:47:44-- https://asinansaglam.github.io/python_bio_2022/files/Spellman.csv Resolving asinansaglam.github.io (asinansaglam.github.io)... 185.199.108.153, 185.199.109.153, 185.199.110.153, ... Connecting to asinansaglam.github.io (asinansaglam.github.io)|185.199.108.153|:443... connected. HTTP request sent, awaiting response... 200 OK Length: 609183 (595K) [text/csv] Saving to: 'Spellman.csv.3' 0K .......... .......... .......... .......... .......... 8% 9.22M 0s 50K .......... .......... .......... .......... .......... 16% 20.2M 0s 100K .......... .......... .......... .......... .......... 25% 16.4M 0s 150K .......... .......... .......... .......... .......... 33% 20.8M 0s 200K .......... .......... .......... .......... .......... 42% 64.9M 0s 250K .......... .......... .......... .......... .......... 50% 16.4M 0s 300K .......... .......... .......... .......... .......... 58% 55.0M 0s 350K .......... .......... .......... .......... .......... 67% 65.5M 0s 400K .......... .......... .......... .......... .......... 75% 8.90M 0s 450K .......... .......... .......... .......... .......... 84% 157M 0s 500K .......... .......... .......... .......... .......... 92% 139M 0s 550K .......... .......... .......... .......... .... 100% 194M=0.02s 2023-10-16 16:47:44 (23.5 MB/s) - 'Spellman.csv.3' saved [609183/609183]
from matplotlib.pylab import cm
import numpy as np
import scipy.cluster.hierarchy as hclust
import matplotlib.pyplot as plt
data = np.genfromtxt('Spellman.csv',skip_header=1,delimiter=',')[:,1:]
Z = hclust.linkage(data,method='complete')
leaves = hclust.leaves_list(Z)
ordered = data[leaves]
plt.matshow(ordered,aspect=0.01,cmap=cm.seismic);
plt.matshow(data,aspect=0.01,cmap=cm.seismic);