Getting the last non-nan index of a sorted numpy matrix or pandas dataframe

Question

Given a numpy array (or pandas dataframe) like this:

import numpy as np

a = np.array([
[1,      1,      1,    0.5, np.nan, np.nan, np.nan],
[1,      1,              


        

Answer 1

This solution doesn't require the array to be sorted. It just returns the last non nan item along axis 1.

(~np.isnan(a)).cumsum(1).argmax(1)