[Numpy-discussion] assigning to submatrix

John Hunter jdhunter at ace.bsd.uchicago.edu
Tue Jul 29 12:58:03 CDT 2003


>>>>> "Perry" == Perry Greenfield <perry at stsci.edu> writes:

    Perry> [Note that I reordered the index arrays to match b; I
    Perry> wasn't sure what was intended]

Yep, I think that was a blooper on my part; to be precise, here is the
matlab code

    a = zeros( 8,8 );
    b = ones( 3,4 );
    rind = [2,4,6];
    cind = [1,4,5,6];

    a(rind, cind) = b;

and the equivalent python

    from Numeric import *

    a = zeros( (8,8) )
    b = ones( (3,4) )
    rind = [1,3,5]
    cind = [0,3,4,5]


    for ia, ib in zip(rind, range(len(rind))):
        for ja, jb in zip(cind, range(len(cind))):
            a[ia,ja] = b[ib,jb]
    print a

And the question is: is there a good way to avoid the double loop
using Numeric?

Thanks,
John




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