NumPy Matrix Multiplication

This can be done by the following three methods.

  1. multiply(): element-wise matrix multiplication.
  2. matmul(): matrix product of two arrays.
  3. dot(): dot product of two arrays.

1. NumPy Matrix Multiplication Element Wise

If you want element-wise matrix multiplication, you can use multiply() function.

import numpy as np

arr1 = np.array([[1, 2],
                 [3, 4]])
arr2 = np.array([[5, 6],
                 [7, 8]])

arr_result = np.multiply(arr1, arr2)

print(arr_result)

Output

2. Matrix Product of Two NumPy Arrays

If you want the matrix product of two arrays, use matmul() function.

import numpy as np

arr1 = np.array([[1, 2],
                 [3, 4]])
arr2 = np.array([[5, 6],
                 [7, 8]])

arr_result = np.matmul(arr1, arr2)

print(f'Matrix Product of arr1 and arr2 is:\n{arr_result}')

arr_result = np.matmul(arr2, arr1)

print(f'Matrix Product of arr2 and arr1 is:\n{arr_result}')

Output

Matrix Product of arr1 and arr2 is:
[[19 22]
 [43 50]]
Matrix Product of arr2 and arr1 is:
[[23 34]
 [31 46]]

3. Dot Product of Two NumPy Arrays

The numpy dot() function returns the dot product of two arrays. The result is the same as the matmul() function for one-dimensional and two-dimensional arrays.

import numpy as np

arr1 = np.array([[1, 2],
                 [3, 4]])
arr2 = np.array([[5, 6],
                 [7, 8]])

arr_result = np.dot(arr1, arr2)

print(f'Dot Product of arr1 and arr2 is:\n{arr_result}')

arr_result = np.dot(arr2, arr1)

print(f'Dot Product of arr2 and arr1 is:\n{arr_result}')

arr_result = np.dot([1, 2], [5, 6])
print(f'Dot Product of two 1-D arrays is:\n{arr_result}')

Output

Dot Product of arr1 and arr2 is:
[[19 22]
 [43 50]]
Dot Product of arr2 and arr1 is:
[[23 34]
 [31 46]]
Dot Product of two 1-D arrays is:
17

Source: digitalocean.com

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