CODEWITHSUNDEEP
pythonnumpy
Borys
Borys

Reputation: 1423

Multiply array of different size

Multiply array of different size.

import numpy as np

a = np.array([1,2,3,4,5])

b = np.array([1,2,3])

print a*b

Ofcourse error:

ValueError: operands could not be broadcast together with shapes (5,) (3,)

Expected result is np.array([1,4,9,0,0])

How to do?

Upvotes: 2

Views: 3811

Answers (3)

John La Rooy
John La Rooy

Reputation: 304157

>>> a = np.array([1,2,3,4,5])
>>> b = np.array([1,2,3])
>>> b.resize(a.shape)
>>> a * b
array([1, 4, 9, 0, 0])

Upvotes: 6

coder hacker
coder hacker

Reputation: 4868

The above answer is correct but to do it without creating a temporary in one line

c=np.append(a,np.zeros(0 if (len(b) - len(a))<0 else (len(b) - len(a))))*np.append(b,np.zeros(0 if (len(a) - len(b))<0 else (len(a) - len(b))))

Upvotes: 0

bjornsen
bjornsen

Reputation: 604

Append a zero array to the smaller array depending on the difference in size:

import numpy as np

a = np.array([1,2,3,4,5])
b = np.array([1,2,3])

diff = len(a) - len(b)

c = np.append(b, np.zeros(diff))

print a*c

Upvotes: 0

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