I have a 2D numpy array that looks like

a = np.array(
    [
        [1,2,np.nan,np.nan],
        [1,33,45,np.nan],
        [11,22,3,78],
    ]
)

I need to extract the last non null value per row i.e. [2, 45, 78]

Please guide on how to get it.

thanks

CodePudding user response：

Break this into two sub-problems.

1. Remove nans from each row
2. Select last element from the array

[r[~np.isnan(r)][-1] for r in a]

produces

[2.0, 45.0, 78.0]

CodePudding user response：

For a vectorial solution, you can try:

# get the index of last nan
idx = np.argmax(~np.isnan(a)[:, ::-1], axis=1)

# slice
a[np.arange(a.shape[0]), a.shape[1]-idx-1]

output: array([ 2., 45., 78.])