Sparse matrix logical indexing

[David Spies]

I'm not sure what it's worth to send this out to the mailing list, but I've finished with sparse-matrix extraction for logical indexing.

ie

A(B) where B is logical and A is sparse behaves appropriately even when A and B are large.

http://hg.octave.org/octave-dspies/graph/

It's the one labeled: Added special-case logical-indexing function

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Note that although this doesn't yet handle assignment with logical indices such as A(B) = C, there's a simple workaround:

A -= A .* B;

[i,j] = find(B);

A += sparse(i,j,C)

gives the same result