Selecting portion of multi-dimensional numpy array

Question

I've searched around but can't seem to find any efficient way to select a portion of a 3d array depending on indices. Lets say for example that I have some 3d array with dimensions 200 x 200 x 200 and I want to select and change the value of all elements where all indices are greater than 100

import numpy as np

mask = np.ones((200,200,200))

for x in np.arange(0,mask.shape[0]):
    for y in np.arange(0,mask.shape[1]):
        for z in np.arange(0,mask.shape[2]):
            if x > 100 & y > 100 & z > 100:
                mask[x,y,z] = 0
            else:
                mask[x,y,z] = 1

There must be some efficient way to do this using np.select or similar but I just can't get my head around it. Any help would be much appreciated.

NPE · Accepted Answer · 2013-01-19 21:15:59Z

4

I want to select and change the value of all elements where all indices are greater than 100

The following should do it:

mask[101:,101:,101:] = 0

edited Jan 19, 2013 at 21:15

answered Jan 19, 2013 at 20:21

NPE

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1 Comment

BrenBarn Over a year ago

Strictly speaking, that will change the values where all indices are greater than or equal to 100.

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