[Numpy-discussion] sort descending with NaNs

[Charles R Harris]

On Thu, Jan 27, 2011 at 9:50 AM, Fabrizio Pollastri <f.pollastri at inrim.it>wrote:

> Hello,
>
> when one has to find a given number of highest values in an array
> containing
> NaNs, the sort function (always ascending) is uncomfortable.
>
> Since numpy >= 1.4.0 NaNs are sorted to the end, so the searched values are
> just
> before the first NaN in a unpredictable position and one has to do another
> search for the first NaN position.
>
> Sorting descending will solve the problem, but there is no option with
> numpy
> sort. There is any other trick to avoid this second search?
>

If you just want to reverse the result, try a[::-1]. I think you may still
need to find the boundaries of the nan's just to make sure they aren't
included among the largest values. Searchsorted is pretty quick in any case.

Chuck
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