change the values of an array from nan to zero

Question

I have an array A on python that has some nan values created by numpy.nan. I want to set all the nan values to zero using A[A==numpy.nan] = 0. It doesn't change the array at all. Why is that?

Answer 1

You want np.isnan:

A[np.isnan(A)] = 0

The problem with your code is that (according to IEEE), nan doesn't equal anything -- even itself.

As a side note, there's also

• np.isinf -> (+/- infinity)
• np.isfinite -> (not infinity or NaN)
• np.isposinf -> (+ infinity)
• np.isneginf -> (- infinity)

Answer 2

You can use the numpy function to change all the nan value at matrix x to zero.

numpy.nan_to_num(x)