Basic Operation ¶

In [9]:

X = 34
Y = 3

In [10]:

X + Y
X - Y
X * Y
X ^ Y
X %% Y
class(X)

37

31

102

39304

1

'numeric'

In [16]:

A = 'Helsinki'
B = 'Warsaw'
C = 'Stockholm'
D = 'Budapest'

In [12]:

class(A)

'character'

In [14]:

v <- c(3, 6, 9, 15)
w <- c(4, 6, 8, 12)

In [15]:

v + w

7
12
17
27

In [17]:

cities <- c(A, B, C, D)

In [18]:

cities

'Helsinki'
'Warsaw'
'Stockholm'
'Budapest'

In [20]:

names(w) <- c(A, B, C, D)

In [21]:

Helsinki: 4
Warsaw: 6
Stockholm: 8
Budapest: 12

In [22]:

w[3]

Stockholm: 8

In [23]:

w['Stockholm']

Stockholm: 8

In [24]:

w[c(2, 3)]

Warsaw: 6
Stockholm: 8

In [25]:

w[c(2:4)]

Warsaw: 6
Stockholm: 8
Budapest: 12

In [26]:

mean(w)

7.5

In [27]:

w > 7

Helsinki: FALSE
Warsaw: FALSE
Stockholm: TRUE
Budapest: TRUE

In [28]:

w[w>7]

Stockholm: 8
Budapest: 12

In [31]:

matrix(1:12, byrow=TRUE, nrow=3)

1	2	3	4
5	6	7	8
9	10	11	12

In [32]:

matrix(1:12, byrow=FALSE, nrow=3)

1	4	7	10
2	5	8	11
3	6	9	12

In [36]:

v <- c(3, 6, 9, 15)
w <- c(4, 6, 8, 12)
v_w <- c(v, w)

In [37]:

v_w

3
6
9
15
4
6
8
12

In [39]:

v_w_mat <- matrix(v_w, byrow=TRUE, nrow=4)

In [40]:

v_w_mat

3	6
9	15
4	6
8	12

Naming Matrix¶

In [41]:

mat_A <- matrix(1:9, byrow=TRUE, nrow=3)
print(mat_A)

     [,1] [,2] [,3]
[1,]    1    2    3
[2,]    4    5    6
[3,]    7    8    9

In [42]:

rownames(mat_A) <- c('Row 1', 'Row 2', 'Row 3')
colnames(mat_A) <- c('Col 1', 'Col 2', 'Col 3')

In [43]:

print(mat_A)

      Col 1 Col 2 Col 3
Row 1     1     2     3
Row 2     4     5     6
Row 3     7     8     9

In [44]:

rowSums(mat_A)

Row 1: 6
Row 2: 15
Row 3: 24

In [46]:

colSums(mat_A)

Col 1: 12
Col 2: 15
Col 3: 18

In [52]:

mat_B = matrix(2:10, byrow = FALSE, nrow = 3)
mat_B

2	5	8
3	6	9
4	7	10

In [53]:

mat_A + mat_B

	Col 1	Col 2	Col 3
Row 1	3	7	11
Row 2	7	11	15
Row 3	11	15	19

In [64]:

mat_A * mat_B

	Col 1	Col 2	Col 3
Row 1	2	10	24
Row 2	12	30	54
Row 3	28	56	90

In [65]:

mat_A / mat_B

	Col 1	Col 2	Col 3
Row 1	0.500000	0.4000000	0.3750000
Row 2	1.333333	0.8333333	0.6666667
Row 3	1.750000	1.1428571	0.9000000

In [ ]:

mat_A %*% mat_B # matrix multiplication

In [55]:

cbind(mat_A, mat_B)

	Col 1	Col 2	Col 3
Row 1	1	2	3	2	5	8
Row 2	4	5	6	3	6	9
Row 3	7	8	9	4	7	10

In [57]:

rbind(mat_A, mat_B)

	Col 1	Col 2	Col 3
Row 1	1	2	3
Row 2	4	5	6
Row 3	7	8	9
	2	5	8
	3	6	9
	4	7	10

Check Workspace¶

In [56]:

ls()

'A'
'B'
'C'
'cities'
'D'
'mat_A'
'mat_B'
'v'
'v_w'
'v_w_mat'
'vector_a'
'vector_b'
'w'
'X'
'Y'

Select Matrix Element¶

In [58]:

mat_C = matrix(1:30, byrow=TRUE, nrow=5)

In [59]:

mat_C

1	2	3	4	5	6
7	8	9	10	11	12
13	14	15	16	17	18
19	20	21	22	23	24
25	26	27	28	29	30

In [60]:

mat_C[,5]

5
11
17
23
29

In [61]:

mat_C[3,]

13
14
15
16
17
18

In [63]:

mat_C[2:5,4]

10
16
22
28

In [ ]: