# [Numpy-discussion] Vectorized percentile function in Numpy (PR #2970)

Sebastian Berg sebastian at sipsolutions.net
Tue Apr 23 18:16:50 EDT 2013

```On Tue, 2013-04-23 at 12:13 -0500, Jonathan Helmus wrote:
>      Back in December it was pointed out on the scipy-user list that
> numpy has a percentile function which has similar functionality to
> scipy's stats.scoreatpercentile.  I've been trying to harmonize these
> two functions into a single version which has the features of both.
>      Scipy PR 374 introduced a version which look the parameters from
> both the scipy and numpy percentile function and was accepted into Scipy
> with the plan that it would be depreciated when a similar function was
> introduced into Numpy.  Then I moved to enhancing the Numpy version with
> Pull Request 2970 .  With some input from Sebastian Berg the
> percentile function was rewritten with further vectorization, but
> neither of us felt fully comfortable with the final product.  Can
> someone look at implementation in the PR and suggest what should be done
> from here?
>

Thanks! For me the main question is the vectorized usage when both
haystack (`a`) and needle (`q`) are vectorized. What I mean is for:

np.percentile(np.random.randn(n1, n2, N), [25., 50., 75.], axis=-1)

I would probably expect an output shape of (n1, n2, 3), but currently
you will get the needle dimensions first, because it is roughly the same
as

[np.percentile(np.random.randn(n1, n2, N), q, axis=-1) for q in [25., 50., 75.]]

so for the (probably rare) vectorization of both `a` and `q`, would it
be preferable to do some kind of long term behaviour change, or just put
the dimensions in `q` first, which should be compatible to the current
list?

Regards,

Sebastian

>   Cheers,
>
>      - Jonathan Helmus
>
>
>  https://github.com/scipy/scipy/pull/374
>  https://github.com/numpy/numpy/pull/2970
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>

```