How to extract finite values of a numpy array without using a loop

Question

I have a numpy array that contains nan and I want to extract only the finite values to get a subarray but without using a loop.

For example:

import numpy as np

z = np.array([2, 3, np.nan, 5])

And I would like to use an instruction such as:

z_cut = z[z != np.nan]

but this doesn't work as it is not possible to compare nan this way.

I could use a loop with instructions such as np.isnan or np.isfinite to get the subarray I want, but I was wondering if there was a more efficient way to do it ?

Does this answer your question? How can I remove Nan from list Python/NumPy — zvone
– zvone, Commented Jul 21, 2020 at 23:47
It is a bit different from my post as the "nan" in the post you shared is not actually NaN value but a string. The accepted answer is closer to what I expected but thank you. — Rhecsu
– Rhecsu, Commented Jul 21, 2020 at 23:54

bigbounty · Accepted Answer · 2020-07-21 23:33:44Z

2

Use ~ operator and np.isnan function

In [23]: import numpy as np
    ...:
    ...: z = np.array([2, 3, np.nan, 5])

In [24]: z[~np.isnan(z)]
Out[24]: array([2., 3., 5.])

In [25]: z_cut = z[~np.isnan(z)]

In [26]: z_cut
Out[26]: array([2., 3., 5.])

answered Jul 21, 2020 at 23:33

bigbounty

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