How do I find the coordinates of nan values in a numpy array?

Question

I tried np.where but without success:

>>>a = np.array([np.nan, 1])
>>>np.where(a == np.nan)
(array([], dtype=int64),)

Answer 1

You need to change

np.where(a == np.nan)

to

np.where(np.isnan(a))

NaN values always return false in equality checks, even with another NaN value. So you need to use special functions to check for NaN like np.isnan.

Answer 2

import numpy as np

x = np.array([0,0,-1,1,np.nan, 0, 1, np.nan])
print np.where(np.isnan(x))

Returns:

(array([4, 7]),)