[Numpy-discussion] subclassing ndarray and keeping same ufunc behavior

Marten van Kerkwijk m.h.vankerkwijk at gmail.com
Tue Nov 15 13:48:11 EST 2016

Hi Stuart,

It certainly seems correct behaviour to return the subclass you
created: after all, you might want to keep the information on
`columns` (e.g., consider doing nanmin along a given axis). Indeed, we
certainly want to keep the unit in astropy's Quantity (which also is a
subclass of ndarray).

On the shape: shouldn't that be print(np.nanmin(r).shape)??

Overall, I think it is worth considering very carefully what exactly
you try to accomplish; if different elements along a given axis have
different meaning, I'm not sure it makes all that much sense to treat
them as a single array (e.g., np.sin might be useful for one column,
not not another). Even if pandas is slower, the advantage in clarity
of what is happening might well be more important in the long run.

All the best,


p.s. nanmin is not a ufunc; you can find it in numpy/lib/nan_functions.py

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