CODEWITHSUNDEEP
pythonnumpy
Aaron
Aaron

Reputation: 27

How to set elemnts of numpy array based on elements of another numpy array

I'm trying to set elemnts of array1 to nan based on elements of array2 which are nan.

The following is my code (which isn't working)

I would greatly appreciate assistance :) 

array1 = np.array([1.,1.,1.,1.,1.,1.,1.,1.,1.,1.])
array2 = np.array([2.,2.,2.,2.,np.nan,np.nan,np.nan,2.,2.,2.])

#I want to create:
#[1.,1.,1.,1.,np.nan,np.nan,np.nan,1.,1.,1.]

# I've tried:
array1[array2 == np.nan] = np.nan
print(array1)
[1. 1. 1. 1. 1. 1. 1. 1. 1. 1.]

Upvotes: 0

Views: 35

Answers (2)

Zabir Al Nazi Nabil
Zabir Al Nazi Nabil

Reputation: 11198

You can use numpy.argwhere to find the indices with np.nan and finally use those indices to change the value of array1.

import numpy as np

array1 = np.array([1.,1.,1.,1.,1.,1.,1.,1.,1.,1.])
array2 = np.array([2.,2.,2.,2.,np.nan,np.nan,np.nan,2.,2.,2.])

inds = np.argwhere(np.isnan(array2))
print(inds)
array1[inds] = np.nan

print(array1)

[[4]
 [5]
 [6]]
[ 1.  1.  1.  1. nan nan nan  1.  1.  1.]

Upvotes: 1

statsman
statsman

Reputation: 86

Use np.isnan.

import numpy as np
array1 = np.array([1.,1.,1.,1.,1.,1.,1.,1.,1.,1.])
array2 = np.array([2.,2.,2.,2.,np.nan,np.nan,np.nan,2.,2.,2.])
array1[np.isnan(array2)] = np.nan
print(array1)

Output is as desired:

[ 1.  1.  1.  1. nan nan nan  1.  1.  1.]

Upvotes: 4

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