[Numpy-discussion] Selecting columns of a matrix
pau.gargallo at gmail.com
Wed Jun 21 13:09:50 EDT 2006
On 6/21/06, Travis Oliphant <oliphant.travis at ieee.org> wrote:
> Johannes Loehnert wrote:
> > Hi,
> >> I'm not sure why bool arrays cannot be used as indices.
> >> The "natural" solution to the original problem seemed to be:
> >> M[:,V>0]
> >> but this is not allowed.
> > I started a thread on this earlier this year. Try searching the archive for
> > "boolean indexing" (if it comes back online somewhen).
> > Travis had some reason for not implementing this, but unfortunately I do not
> > remember what it was. The corresponding message might still linger on my home
> > PC, which I can access this evening....
> I suspect my reason was just not being sure if it could be explained
> consistently. But, after seeing this come up again. I decided it was
> easy enough to implement.
> So, in SVN NumPy, you will be able to do
> The V>0 will be replaced with integer arrays as if nonzero(V>0) had been
does it work for a[<boolean>,<boolean>] ?
what about a[ix_( nonzero(<boolean>), nonzero(<boolean>) )] ?
maybe the <boolean> to nonzero(<boolean>) conversion would be more
coherently done by the ix_ function than by the 
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