[Numpy-discussion] Would it be possible to enhance np.unique(.) with a keyword kind

[eat]

Hi,

On Tue, Dec 20, 2011 at 3:41 AM, <josef.pktd at gmail.com> wrote:

> On Mon, Dec 19, 2011 at 8:16 PM, eat <e.antero.tammi at gmail.com> wrote:
> > Hi,
> >
> > On Tue, Dec 20, 2011 at 2:33 AM, <josef.pktd at gmail.com> wrote:
> >>
> >> On Mon, Dec 19, 2011 at 6:27 PM, eat <e.antero.tammi at gmail.com> wrote:
> >> > Hi,
> >> >
> >> > Especially when the keyword return_index of np.unique(.) is specified
> to
> >> > be
> >> > True, would it in general also be reasonable to be able to specify the
> >> > sorting algorithm of the underlying np.argsort(.)?
> >> >
> >> > The rationale is that (for at least some of my cases) higher level
> >> > algorithms seems to be too over complicated unless I'm not able to
> >> > request a
> >> > stable sorting order from np.unique(.)
> (like np.unique(., return_index=
> >> > True, kind= 'mergesort').
> >> >
> >> > (FWIW, I apparently do have a working local hack for this kind of
> >> > functionality, but without extensive testing of 'all' corner cases).
> >>
> >> Just to understand this:
> >>
> >> Is the return_index currently always the first occurrence or random?
> >
> > No, for current implementation it's not always the first occurrence
> > returned. AFAIK, the only stable algorithm to provide this is
> ' mergesort'
> > and that's why I'll like to have a keyword 'kind' to propagate down to
> then
> > internals.
>
> Thanks, then I'm all in favor of mergesort.
>
> >>
> >>
> >> I haven't found a use for return_index yet (but use return_inverse a
> >> lot), but if we are guaranteed to get the first instance, then this
> >> could be very useful.
> >
> > I think that 'return_inverse' will suffer of the same
> > nondeterministic behavior as well.
>
> I don't think so, because there is a unique mapping from observations
> to unique items.
>
But (source code of 1.6.1) indicates that keywords 'return_inverse' are
'return_index' are related, indeed.

Just my 2 cents
eat

>
> Josef
>
> >
> > Thanks,
> > eat
> >>
> >>
> >> Josef
> >>
> >>
> >> >
> >> >
> >> > Thanks,
> >> > eat
> >> >
> >> > _______________________________________________
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> >> >
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> >
> >
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