Size of the unique elements and size of the output of accumarray

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Snoopy
Snoopy 2021-8-8
评论： Snoopy 2021-8-8
Why are the sizes of the two arrays, unique and accumarray, not the same?
size(unique(MAT(:,1)))
size(accumarray(MAT(:,1),MAT(:,2)))

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Matt J
Matt J 2021-8-8
编辑：Matt J 2021-8-8
Ran in:
They will only be the same size if unique(MAT(:,1)) consists of consecutive integers starting from 1. Otherwise, accumarray must leave certain spots blank. A simpler example:
accumarray([2;4],1)
ans = 4×1
0 1 0 1

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