How to mask numpy 2D array by index?

Question

I have a numpy 2D array with a range of 800. Now I only want to use the elements from index range 600 to 700 and set all other values to np.nan. The Index of the lasting elements should be the same as before. The length of the array should be the same too. Thanks!

Please show a minimal reproducible example.

mcsoini
– mcsoini

2021-11-21 11:31:14 +00:00
Commented Nov 21, 2021 at 11:31 — mcsoini
– mcsoini, Commented Nov 21, 2021 at 11:31

Eric Marchand · Accepted Answer · 2021-11-21 11:40:45Z

1

import numpy as np
a = np.random.random ([800,4])

a[:600, :], a[700:, :] = np.nan, np.nan

answered Nov 21, 2021 at 11:40

Eric Marchand

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2 Comments

Jeremy Caney Over a year ago

@denali11: Please be sure to mark it as the accepted answer in that case. You can do that by clicking the check mark next to the answer.

joanis Over a year ago

This is an excellent answer, but I find combining tuple unpacking with broadcasting a little confusing. Just to make the code a little more readable, I would use the equivalent two statements a[:600, :] = np.nan followed by a[700:, :] = np.nan instead.

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