Lines in Lets-Plot¶

In [1]:

%useLatestDescriptors
// %use krangl
%use kotlin-statistics
%use lets-plot

In [2]:

LetsPlot.getInfo()  // This prevents Krangl from loading an obsolete version of Lets-Plot classes.

Out[2]:

Lets-Plot Kotlin API v.4.1.1. Frontend: Notebook with dynamically loaded JS. Lets-Plot JS v.2.5.1.

In [3]:

%use krangl

Vertical, horizontal and oblique lines¶

In [4]:

val mpgDf = DataFrame.readCSV("https://raw.githubusercontent.com/JetBrains/lets-plot-kotlin/master/docs/examples/data/mpg.csv")
mpgDf.head()

Out[4]:

	manufacturer	model	displ	year	cyl	trans	drv	cty	hwy	fl	class
1	audi	a4	1.8	1999	4	auto(l5)	f	18	29	p	compact
2	audi	a4	1.8	1999	4	manual(m5)	f	21	29	p	compact
3	audi	a4	2.0	2008	4	manual(m6)	f	20	31	p	compact
4	audi	a4	2.0	2008	4	auto(av)	f	21	30	p	compact
5	audi	a4	2.8	1999	6	auto(l5)	f	16	26	p	compact

Shape: 5 x 12.

In [5]:

val mpgMap = mpgDf.toMap()

In [6]:

val regModel = (mpgMap["cty"]!! zip mpgMap["hwy"]!!).simpleRegression(
    xSelector = { it.first as Number },
    ySelector = { it.second as Number }
)
val ctyMedian = mpgDf.get("cty").median()
val hwyMedian = mpgDf.get("hwy").median()

In [7]:

letsPlot(mpgMap) { x = "cty"; y = "hwy" } +
    geomPoint() +
    geomVLine(xintercept = ctyMedian, color = "#756bb1", linetype = "dashed") +
    geomHLine(yintercept = hwyMedian, color = "#756bb1", linetype = "dashed") +
    geomABLine(slope = regModel.slope, intercept = regModel.intercept, color = "#de2d26") +
    themeMinimal()

Out[7]:

Broken lines¶

In [8]:

fun generateParabolicDataMap(n: Int = 25, a: Double = 1.0): Map<String, List<Double>> {
    val rand = java.util.Random(42)
    val x = List(2 * n + 1) { i -> a * (i - n).toDouble() / n }
    val y = x.map { i -> i * i + rand.nextGaussian() }
    return mapOf("x" to x, "y" to y)
}

val pDataMap = generateParabolicDataMap(a = 3.0)

In [9]:

letsPlot(pDataMap) + geomLine() { x = "x"; y = "y" }

Out[9]:

In [10]:

letsPlot(pDataMap) + geomPath() { x = "x"; y = "y" }

Out[10]:

In [11]:

letsPlot(pDataMap) + geomStep() { x = "x"; y = "y" }

Out[11]:

And what is the difference between geomLine() and geomPath()?

Let's have a look at the following example:

In [12]:

fun generateArchimedeanDataMap(n: Int = 25, k: Double = 1.0, a: Double = 1.0): Map<String, List<Double>> {
    val phi = List(n) { i -> 2.0 * PI * k * i.toDouble() / (n - 1) }
    val r = phi.map { angle -> (a * angle) / (2.0 * PI) }
    val x = (r zip phi).map { p -> p.first * cos(p.second) }
    val y = (r zip phi).map { p -> p.first * sin(p.second) }
    return mapOf("x" to x, "y" to y)
}

val aDataMap = generateArchimedeanDataMap(n = 200, k = 2.0)

In [13]:

letsPlot(aDataMap) +
    geomLine() { x = "x"; y = "y" } +
    ggtitle("Plotting with geomLine()")

Out[13]:

In [14]:

letsPlot(aDataMap) +
    geomPath() { x = "x"; y = "y" } +
    ggtitle("Plotting with geomPath()")

Out[14]:

Also an interesting plot could be drawed with geomSegment():

In [15]:

letsPlot(generateArchimedeanDataMap(n = 50)) + geomSegment(xend = 0.0, yend = 0.0) { x = "x"; y = "y" }

Out[15]: