Limit the number of elements in each row of matrix using Numpy Python

Question

I have following numpy matrix:

import numpy as np
matrix = np.array([[1,2,3],[4,5,6]])

and a numpy vector:

vector = np.array([1,2])

where each element in the vector represents for each row of the matrix, the number of elements I want to retain. I would like to replace all other elements in the matrix with 0.

The final matrix should look like:

matrix_output = np.array([[1,0,0],[4,5,0]])

What is the quickest way ?

flakes · Accepted Answer · 2021-04-23 02:14:45Z

2

Could do something simple like this:

import numpy as np

matrix = np.array([[1,2,3],[4,5,6]])
vector = np.array([1,2])

for row, index in enumerate(vector):
    matrix[row, index:] = 0

print(matrix)

[[1 0 0]
 [4 5 0]]

answered Apr 23, 2021 at 2:14

flakes

24.1k8 gold badges52 silver badges101 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

hpaulj · Accepted Answer · 2021-04-23 06:22:40Z

1

try

mask = vector[:,None]<=np.arange(3)
matrix[mask] = 0

answered Apr 23, 2021 at 6:22

hpaulj

233k14 gold badges260 silver badges392 bronze badges

Collectives™ on Stack Overflow

Limit the number of elements in each row of matrix using Numpy Python

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related