Find index of middle 1 in a logical row

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Abbas Husain
Abbas Husain 2021-3-17
回答： Image Analyst 2021-4-2
I have A = [ 0 0 0 1 1 1 0 0 0]
I'm trying to get as an output the index of the middle nonzero 1 entry - in this case: 5.
Thank you :)
  1 个评论
John D'Errico
John D'Errico 2021-3-17
Confusing question. Are you just trying to find the index of the middle element? Simple:
n = numel(A);
middleind = ceil(n/2);
Of course, if you have an even number of elements, the middle index is ambiguous.
Do you know there are elements SOMEWHERE ROUGHLY in the middle, and you want to find the index of the middle of those leements that are 1? Again, what if there are an even number of unit elements?
What happens if there is more than one group of unit elements?
Until you explain/understand what you really need to do, in all circumstances, you cannot solve a problem.

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回答（1 个）

Image Analyst
Image Analyst 2021-4-2
You can use regionprops:
A = [ 0 0 0 1 1 1 0 0 0 1 1 1 1 0] % Two regions
props = regionprops(logical(A), 'Centroid')
xy = vertcat(props.Centroid)
centroidIndexes = xy(:, 1)
for this example, you'll get two centroids:
centroidIndexes =
5
11.5

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