How to create dot product of two arrays in using numpy.dot() function
In this article, you will learn how to create dot product of two arrays in using numpy.dot() function.
Syntax: numpy.dot(a, b, out=None)
Dot product of two arrays. Specifically,
If both a and b are 1-D arrays, it is inner product of vectors (without complex conjugation).
If both a and b are 2-D arrays, it is matrix multiplication, but using matmul or a @ b is preferred.
If either a or b is 0-D (scalar), it is equivalent to multiply and using numpy.multiply(a, b) or a * b is preferred.
If a is an N-D array and b is a 1-D array, it is a sum product over the last axis of a and b.
If a is an N-D array and b is an M-D array (where M>=2), it is a sum product over the last axis of a and the second-to-last axis of b:
dot(a, b)[i,j,k,m] = sum(a[i,j,:] * b[k,:,m])
Parameters:
a : array_like
First argument.
b : array_like
Second argument.
out : ndarray, optional
Output argument. This must have the exact kind that would be returned if it was not used. In particular, it must have the right type, must be C-contiguous, and its dtype must be the dtype that would be returned for dot(a,b). This is a performance feature. Therefore, if these conditions are not met, an exception is raised, instead of attempting to be flexible.
Returns:
output : ndarray
Returns the dot product of a and b. If a and b are both scalars or both 1-D arrays then a scalar is returned; otherwise an array is returned. If out is given, then it is returned.
Raises:
ValueError
If the last dimension of a is not the same size as the second-to-last dimension of b.
#example program on np.dot() function
import numpy as np
print('single array result\n',np.dot(3, 4))
# two dimentionl array
a=np.array([[1, 2], [ 5, 6]])
b=np.array([[1, 4], [ 5, 8]])
print(a.shape)
print(b.shape)
c=np.dot(a,b)
print('two dimentionl arrayresult\n',c)
# three dimentionl array
a=np.array([[1, 2,3], [4, 5, 6], [7,8,9]])
b=np.array([[1, 2,3], [4, 5, 6], [7,8,9]])
print(a.shape)
print(b.shape)
c=np.dot(a,b)
print('three dimentionl arrayresult\n',c)
