[Numpy-discussion] Selecting columns of a matrix
oliphant.travis at ieee.org
Wed Jun 21 11:52:24 EDT 2006
Bill Baxter wrote:
> On 6/21/06, *Simon Burton* <simon at arrowtheory.com
> <mailto:simon at arrowtheory.com>> wrote:
> On Wed, 21 Jun 2006 13:48:48 +0900
> "Bill Baxter" <wbaxter at gmail.com <mailto:wbaxter at gmail.com>> wrote:
> > >>> a[:,num.where(v>0.5)]
> > array([[1, 2, 4],
> > [6, 7, 9]])
> > I'll put that up on the Matlab->Numpy page.
> oh, yuck. What about this:
> >>> a[:,num.nonzero(v>0.5)]
> array([[0, 1, 3],
> [5, 6, 8]])
> The nonzero() function seems like kind of an anomaly in and of
> itself. It doesn't behave like other index-returning numpy
> functions, or even like the method version, v.nonzero(), which returns
> the typical tuple of array. So my feeling is ... ew to numpy.nonzero.
How about we add the ability so that
a[:, <boolean>] gets translated to
a[:, nonzero(<boolean>)] ?
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