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np.abs(DeltaTime(dts)) returns object np.array not DeltaTime(abs(dts)) #10653
Description
Description
Using np.abs() on a DeltaTime object does not return the expected result.
Expected behavior
In [4]: dt = TimeDelta([-1, 1]*u.day)
In [5]: np.abs(dt)
Out[5]:
<TimeDelta object: scale='None' format='jd' value=[1. 1.]>
Actual behavior
In [4]: dt = TimeDelta([-1, 1]*u.day)
In [5]: np.abs(dt)
Out[5]:
array([<TimeDelta object: scale='None' format='jd' value=1.0>,
<TimeDelta object: scale='None' format='jd' value=1.0>],
dtype=object)
Steps to Reproduce
See above.
System Details
Darwin-19.5.0-x86_64-i386-64bit
Python 3.7.7 (default, Mar 26 2020, 10:32:53)
[Clang 4.0.1 (tags/RELEASE_401/final)]
Numpy 1.18.1
astropy 4.2.dev518+g5dfce215b.d20200813
Scipy 1.4.1
Matplotlib 3.1.3
Activity
mhvk commentedon Aug 13, 2020
Arrgghh. To get this to work we need to implement
__array_ufunc__- not super-hard.Note that
absdoes work (since that just uses the method):mhvk commentedon Aug 13, 2020
p.s. Right now, for the same reason,
np.add,np.subtract, etc.,do not work eithercreate object arrays as well.Antetokounpo commentedon Sep 27, 2020
I've written a quick and dirty implementation of
__array_ufunc__and although it fixes the problemsnp.add, np.abs,, etc., it creates a whole lot of new ones. For example:The expected behavior in this case would be that the returned result is a
TimeDeltaand not aQuantity. But I've noticed that this happens only if__array_ufunc__is defined, even if it's only a simplepass(and it doesn't get called anyway). I haven't been able to track down why it happens though.So it seems that if we're going to implement
__array_ufunc__to fix this issue, we also need to modify howQuantityobjects (and maybe others) interact withTimeDelta.mhvk commentedon Sep 27, 2020
@Antetokounpo - Right now, without
Time.__array_ufunc__, the quantity version never gets called becauseTime.__array_priority__is defined and is higher thanQuantity.__array_priority__. But if you do defineTime.__array_ufunc__, then the priorities no longer get checked.But you did find a bug:
Quantity.__array_ufunc__should returningNotImplementedfor anyTimeinput, as it does not know how to deal with those. I raised #10776.mhvk commentedon Sep 28, 2020
Note that @maxnoe has also started to implement
Time.__array_ufunc__- see #10272.