NaN values

1. Scikit-learn will not accept np.nan values. Take array_3 as follows:

array_3 = np.array([np.nan, 0, 1, 2, np.nan])

1. Find the NaN values with a special Boolean array created by the np.isnan function:

np.isnan(array_3)
array([ True, False, False, False,  True], dtype=bool)

1. Filter the NaN values by negating the Boolean array with the symbol ~ and placing brackets around the expression:

array_3[~np.isnan(array_3)]
>array([ 0.,  1.,  2.])

1. Alternatively, set the NaN values to zero:

array_3[np.isnan(array_3)] = 0
array_3
array([ 0.,  0.,  1.,  2.,  0.])