[Numpy-discussion] indexing with booleans without making a copy?

Ernest Adrogué eadrogue@gmx....
Wed Sep 8 15:00:38 CDT 2010


 8/09/10 @ 15:35 (-0400), thus spake Anne Archibald:
> 2010/9/8 Ernest Adrogué <eadrogue@gmx.net>:
> > I have a sorted, flat array:
> >
> > In [139]: a =np.array([0,1,2,2,2,3])
> >
> > Basically, I want views of the areas where there
> > are repeated numbers (since the array is sorted, they
> > will be contiguous).
> >
> > But, of course, to find the numbers that are repeated
> > I have to use comparison operations that return
> > boolean arrays, so I suppose the problem is converting
> > the boolean array into a slice.
> 
> Well, you're going to have to do some allocation, but how's this? Use
> unique1d to get an array of unique values. Then use searchsorted
> twice, once to find the leftmost end of each hunk, and once to find
> the rightmost end of each hunk.

I like it. Thanks :)

> 
> Anne
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