Matrix Rotation

Rotate matrices for 90, 180, or 270 degrees..

rot90(a, k = 1)

Arguments

a

numeric or complex matrix

k

scalar integer number of times the matrix will be rotated for 90 degrees; may be negative.

Details

Rotates a numeric or complex matrix for 90 (k = 1), 180 (k = 2) or 270 (k = 3 or k = -1) degrees.

Value of k is taken mod 4.

Value

the original matrix rotated

Examples

a <- matrix(1:12, nrow=3, ncol=4, byrow=TRUE)
rot90(a)
#>      [,1] [,2] [,3]
#> [1,]    4    8   12
#> [2,]    3    7   11
#> [3,]    2    6   10
#> [4,]    1    5    9
rot90(a, 2)
#>      [,1] [,2] [,3] [,4]
#> [1,]   12   11   10    9
#> [2,]    8    7    6    5
#> [3,]    4    3    2    1
rot90(a, -1)
#>      [,1] [,2] [,3]
#> [1,]    9    5    1
#> [2,]   10    6    2
#> [3,]   11    7    3
#> [4,]   12    8    4