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How can a logical vector be converted to a numeric vector in which the values represent the number of zeros between ones?

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Robert
Robert on 9 Nov 2016
Edited: Stephen Cobeldick on 8 Dec 2016
I am searching for a simple way to convert a logical vector, to a vector in which the values represent the total number scalars between ones, and including the first 1 in the list. Essentially converting x to y where:
x = [1;1;1;0;0;1;0;1];
y = [1;1;3;3;3;2;2;1];
Any suggestions? Thanks!
RTT

Accepted Answer

Ahmet Cecen
Ahmet Cecen on 10 Nov 2016
Edited: Ahmet Cecen on 10 Nov 2016
Something along the lines of:
x = [1;1;1;0;0;1;0;1];
inds = find(x);
diffs = [inds(2:end);0]-inds;
diffs(end) = 1;
y = repelem(diffs, diffs); % By Guillaume
  2 Comments
Ahmet Cecen
Ahmet Cecen on 10 Nov 2016
Wow! What a nice function that I had never heard of. Super useful.
The example in the question is basically using the 1's in the matrix as nodes, and the 0's between 1's as the edge weights.
The algorithm is first finding where the ones are, then finds the distance between them ([inds(2:end);0] is aligning the next index with current for the subtraction.). It is a similar effect to circshift, but I didn't want to confuse the reader with periodicity when it is not used here. Last element is set to 1 simply assuming the list ends with a 1, as it is unclear from the question how a list ending with a 0 would be treated.

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