How to rotate a matrix?

Let’s learn how to rotate a matrix in Numpy. We are going to see a few tricks in that matter.

With Numpy it is very easy to rotate matrix 90 degrees. There is dedicated rot90 Numpy method.

import numpy as np

my_array = np.array([[11, 12, 13],
                    [21, 22, 23],
                    [31, 32, 33]])
print(f"This is my array: \n{my_array}")

rotate_array = np.rot90(my_array)
print(f"Array rotated:  \n{rotate_array}")

To rotate 270 degrees just add 3 as a parameter to rot90 function. This parameter makes 3 rounds of 90 degrees rotation (counter clockwise).

import numpy as np

my_array = np.array([[11, 12, 13],
                    [21, 22, 23],
                    [31, 32, 33]])
print(f"This is my array: \n{my_array}")

rotate_array = np.rot90(my_array, 3)
print(f"Array rotated 270 degrees:  \n{rotate_array}")

This is 270 degrees rotation but we can also say that this is left rotation because this is how to rotate an matrix left direction.

To rotate 180 put np.rot90(my_array, 2). Having np.rot90(my_array, 4) will not change the array at all.

You can also rotate an array over the axes.

import numpy as np

my_array = np.array([[11, 12, 13],
                    [21, 22, 23],
                    [31, 32, 33]])
print(f"This is my array: \n{my_array}")

rotate_array = np.rot90(my_array, axes=(1, 0))
print(f"Array rotated over axes=(1, 0):  \n{rotate_array}")

I used np.rot90(my_array, axes=(1, 0)) and this is how it got rotated.