Problem 320. Maintain shape of logical-index mask
When using logical indexing into an array, MATLAB returns a vector output. For example, if
A = magic(3);
mask = logical([0 1 1; 0 1 1; 0 1 1]);
then
out=A(mask)
returns the output
out =
1 5 9 6 7 2
But when the mask has a block format (as in this example), it is sometimes desirable to maintain that block shape in the output. So, in this case, the desired output would be
out =
1 6 5 7 9 2
In other words, the output is the same shape as the logical index block.
The (first) input array A will be two-dimensional, and the (second) input array mask will be a logical that is guaranteed to have the block characteristic.
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3 Comments
More tests. A lot of solutions assume that mask has only 2 columns.
Good suggestion. I've added a couple more tests to the suite, including one that has three columns in the logical mask.
Is there a way to just view the solution to this? I've been trying to do this for my own work, and this problem is the only thing I've found that purports to do what I need, but of course it doesn't actually tell me how.
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