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Duplicate minimal entries in interpolate.interp1d result in nan

See original GitHub issue

interpolate.interp1d returns nan in the following example for me (scipy version is 0.14.0):

In [7]: f = interpolate.interp1d([0, 0, 1], [0, 0, 1], kind='linear')
In [8]: f(0)
 /home/jmetzen/.anaconda/lib/python2.7/site-packages/scipy/interpolate/interpolate.py:445: RuntimeWarning: invalid value encountered in true_divide
 slope = (y_hi - y_lo) / (x_hi - x_lo)[:, None]
Out[8]: array(nan)

Everything works fine in the case without duplicates:

In [13]: f = interpolate.interp1d([0, 1], [0,  1], kind='linear')
In [14]: f(0)
Out[14]: array(0.0)

Duplicating any other entry besides the minimal one seems to be ok. I guess this is a bug?

Issue Analytics

State:
Created 9 years ago
Reactions:1
Comments:13 (11 by maintainers)

Top GitHub Comments

1reaction

argriffingcommented, Dec 26, 2014

The docs say

See also
UnivariateSpline -- A more recent wrapper of the FITPACK routines.

Would it make sense to officially deprecate interp1d so that it raises a deprecation warning?

Edit: never mind, I see that interp1d clones a matlab function, so it will live forever.

0reactions

ev-brcommented, Aug 5, 2019

We won’t be deprecating interp1d any time soon it seems. Handling of duplicate values is also best left as is, cf. gh-9886. Looks like there’s not much to do here, thus closing. Thanks @jmetzen, all.

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