ENH: Adding where for argmin

[negedng]

Similar to amin's new initial and where parameters, argmin should have options to mask too.
Thanks!

Reproducing code example:

import numpy as np
def argmin(a, initial=None, where=None):
    if where is None:
        return np.argmin(a)
    if initial is None:
        raise("To use a where mask one has to specify 'initial'")
    return np.argmin([a[i] if where[i] else initial for i in range(len(a))])

[m10an]

Could I work on this?

[carlosgmartin]

@m10an @seberg I'm also interested in this feature. Do you know what remains to be done to add it?

[m10an]

@carlosgmartin I think you can pick up my work, which is mostly about passing arguments and type hints, except changes here