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How to multiply matrices in NumPy

Two matrices are compatible for multiplication if the number of columns of 1 matrix is equal to the number of rows of the other matrix.

For example, if matrix 1 has dimensions a * N and matrix 2 has dimensions N * b, then the resulting matrix has dimensions of a * b.

The illustration below shows how this is done:

1 of 2

To multiply two matrices use the dot() function of NumPy. It takes only 2 arguments and returns the product of two matrices.

Syntax

The general syntax is :

np.dot(x,y)


where x and y are two matrices of size a * M and M * b, respectively.

Code

The following code shows an example of multiplying matrices in NumPy:

import numpy as np
# two dimensional arrays
m1 = np.array([[1,4,7],[2,5,8]])
m2 = np.array([[1,4],[2,5],[3,6]])
m3 = np.dot(m1,m2)
print(m3)

# three dimensional arrays
m1 = ([1, 6, 5],[3 ,4, 8],[2, 12, 3])
m2 = ([3, 4, 6],[5, 6, 7],[6,56, 7])
m3 = np.dot(m1,m2)
print(m3)


RELATED TAGS

numpy
python
multiplication