Removing columns which has only nan values from a NumPy array

2024/9/27 9:26:05

I have a NumPy matrix like the one below:

[[182 93 107 ..., nan nan -1][182 93 107 ..., nan nan -1][182 93 110 ..., nan nan -1]..., [188 95 112 ..., nan nan -1][188 97 115 ..., nan nan -1][188 95 112 ..., nan nan -1]]

I want to remove the columns which only involve nan values from the above matrix.

How can I do this? Thanks.

Answer

Assuming your array is of floats now, you can identify all the columns which are NaN and use fancy indexing to retrieve the others:

d
array([[ 182.,   93.,  107.,   nan,   nan,   -1.],[ 182.,   93.,  107.,    4.,   nan,   -1.],[ 182.,   93.,  110.,   nan,   nan,   -1.],[ 188.,   95.,  112.,   nan,   nan,   -1.],[ 188.,   97.,  115.,   nan,   nan,   -1.],[ 188.,   95.,  112.,   nan,   nan,   -1.]])d[:,~np.all(np.isnan(d), axis=0)]array([[ 182.,   93.,  107.,   nan,   -1.],[ 182.,   93.,  107.,    4.,   -1.],[ 182.,   93.,  110.,   nan,   -1.],[ 188.,   95.,  112.,   nan,   -1.],[ 188.,   97.,  115.,   nan,   -1.],[ 188.,   95.,  112.,   nan,   -1.]])

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