[Numpy-discussion] converting discrete data to unique integers

Neil Crighton neilcrighton at gmail.com
Wed Nov 4 17:23:05 EST 2009

 <josef.pktd <at> gmail.com> writes:

> > Good point. With the return_inverse solution, is unique() guaranteed
> > to give back the same array of unique values in the same (presumably
> > sorted) order? That is, for two arrays A and B which have elements
> > only drawn from a set S, is all(unique(A) == unique(B)) guaranteed?
> > The code is a quite clever and a bit hard to follow, but it *looks*
> > like it will provide a stable mapping since it's using a sort.
> I looked at it some time ago, and from what I remember, the sort
> is done if return_inverse=True but for some codepath it uses
> set.

unique always sorts, even if it uses set. So I'm pretty sure 
all(unique(A) == unique(B)) is guaranteed.


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