suggestions for slices of matrices

JJ josh8912 at yahoo.com
Tue Oct 10 01:17:28 CDT 2006


Hello.
I haven't been following development too closely
lately, but I did just download and reinstall the
current svn version.  For what its worth, I would like
to again suggest two changes:

--  If M is a nxm matrix and P and Z are nx1 (or 1xn)
matrices, then it would be nice if we could write
M[P==Z,:] to obtain all columns and only those rows
where P==Z.  Likewise, for 1xm (or mx1) matrices U and
V, it would be nice to be able to use M[P==Z,U==V]. 
Also, it would be nice to use M[P==Z,U==2], for
example, to obtain selected rows where matrix U is
equal to a constant.

--  It would be nice to slice a matrix by using
M[[1,2,3],[3,5,7]], for example.

I believe this would help make indexing more user
friendly.  In my humble opinion, I think indexing is a
weak spot in numpy.  I find that most of my debugging
involves finding the right code to make a matrix slice
the way I want it.

John




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