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ENH: add support for array-likes in polynomial evaluation #18662

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ENH: add support for array-likes in polynomial evaluation #18662

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5787098
add asarray to polybase call method
Mar 21, 2021
741b0be
add release note
Mar 21, 2021
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5 changes: 5 additions & 0 deletions doc/release/upcoming_changes/18662.new_feature.rst
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@@ -0,0 +1,5 @@
Add support for array-likes in polynomial evaluation
----------------------------------------------------------------------------

Polynomial evaluation now accepts array-likes (e.g. lists) as its
input argument, in addition to NumPy arrays.
1 change: 1 addition & 0 deletions numpy/polynomial/_polybase.py
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Expand Up @@ -479,6 +479,7 @@ def __setstate__(self, dict):

def __call__(self, arg):
off, scl = pu.mapparms(self.domain, self.window)
arg = np.asarray(arg)
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With this, previously working calls using masked arrays would stop working - e.g.,

np.polynomial.Polynomial([1, 2])(np.ma.MaskedArray([3, 4], mask=[True, False]))

That particular part could be solved by making this np.asanyarray - though I guess it is possible the polynomials are also used by, e.g., dask, in which case this would still be a problem.

arg = off + scl*arg
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A simpler way to do the same thing might be to make sure scl is an array scalar rather than a regular scalar, since array * list already has the right behaviour of interpreting this list as an array. One can do it here by writing this as off + scl[...] * arg - though it might make more sense to ensure scl is an array scalar inside mapparms.

return self._val(arg, self.coef)

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