Matrix or Array Rotation by 90 Degrees

`rotate90(img, direction = "positive")`

- img
an array or a matrix

- direction
The direction of rotation by 90 degrees. The value can be

`"positive"`

(default) or`"negative"`

. Aliases are`"counterclockwise"`

and`"clockwise"`

, respectively.

an array or a matrix (rotated by 90 degrees)

The function takes an array or matrix as input
object (`img`

) and returns the object rotated by
90 degrees. Per default, the rotation is done in the
mathematically positive direction (i.e.,
counterclockwise). Clockwise rotation (i.e.,
mathematically negative) can be specified by passing
the value `"negative"`

to the `direction`

argument.

```
# sample matrix
img <- matrix(1:6, ncol = 2)
img
#> [,1] [,2]
#> [1,] 1 4
#> [2,] 2 5
#> [3,] 3 6
rotate90(img) # counterclockwise
#> [,1] [,2] [,3]
#> [1,] 4 5 6
#> [2,] 1 2 3
rotate90(img, direction = "negative") # clockwise
#> [,1] [,2] [,3]
#> [1,] 3 2 1
#> [2,] 6 5 4
```