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POTurning a binary matrix into a vector of the last nonzero index in a fast, vectorized fashion
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831721
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2009-05-06T20:59:14.957
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2017-05-07T05:57:45.180
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2017-05-07T05:57:45.180
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text
Body
Suppose, in MATLAB, that I have a matrix, A, whose elements are either 0 or 1. How do I get a vector of the index of the last non-zero element of each column in a faster, vectorized way? I could do <code>[B, I] = max(cumsum(A));</code> and use <code>I</code>, but is there a faster way? (I'm assuming cumsum would cost a bit of time even suming 0's and 1's). Edit: I guess that I vectorized even more than I need fast - Mr. Fooz' loop is great but each loop in MATLAB seems to cost me a lot in debugging time even if it is fast. 
Tags
<matlab><matrix><vector><vectorization>
Title
Turning a binary matrix into a vector of the last nonzero index in a fast, vectorized fashion
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1. USgnovice
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1. USJoe Soul-bringer
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