On Mon, Aug 31, 2015 at 1:23 AM, Sebastian Berg
That would be my gut feeling as well. Returning `NaN` could also make sense, but I guess we run into problems since we do not know the input type. So `None` seems like the only option here I can think of right now.
My inclination is that return NaN would be the appropriate choice. It's certainly consistent with the behavior for float dtypes -- my expectation for object dtype behavior is that it works exactly like applying the np.sign ufunc to each element of the array individually. On the other hand, I suppose there are other ways in which an object can fail all those comparisons (e.g., NaT?), so I suppose we could return None. But it would still be a weird outcome for the most common case. Ideally, I suppose, np.sign would return an array with int-NA dtype, but that's a whole different can of worms... Stephan