[Numpy-discussion] argmax() indexes to value

Elliot Hallmark Permafacture at gmail.com
Thu Oct 31 00:42:34 EDT 2019


I wouldn't be surprised at all if calling max in addition to argmax wasn't
as fast or faster than indexing the array using argmax. Regardless, just
use that then profile when you're done with the whole thing and see if
there's any gains to be made. Very likely not here.

-elliot

On Wed, Oct 30, 2019, 10:32 PM Daniele Nicolodi <daniele at grinta.net> wrote:

> On 30/10/2019 19:10, Neal Becker wrote:
> > max(axis=1)?
>
> Hi Neal,
>
> I should have been more precise in stating the problem. Getting the
> values in the array for which I'm looking at the maxima is only one step
> in a more complex piece of code for which I need the indexes along the
> second axis of the array. I would like to avoid to have to iterate the
> array more than once.
>
> Thank you!
>
> Cheers,
> Dan
>
>
> > On Wed, Oct 30, 2019, 7:33 PM Daniele Nicolodi <daniele at grinta.net
> > <mailto:daniele at grinta.net>> wrote:
> >
> >     Hello,
> >
> >     this is a very basic question, but I cannot find a satisfying answer.
> >     Assume a is a 2D array and that I get the index of the maximum value
> >     along the second dimension:
> >
> >     i = a.argmax(axis=1)
> >
> >     Is there a better way to get the value of the maximum array entries
> >     along the second axis other than:
> >
> >     v = a[np.arange(len(a)), i]
> >
> >     ??
> >
> >     Thank you.
> >
> >     Cheers,
> >     Daniele
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