How to pick the elements in a vector with row coordinates satisfying a criterion determined by another vector?

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MRC
MRC 2013-11-28
回答： Andrei Bobrov 2013-11-28
Hi, I have a column vector A reporting the first m natural numbers, each of them repeated an arbitrary number of times, e.g.
A=[1;1;2;2;2;3;4;4;4;4];
and a column vector B reporting the first n natural numbers, n>=m, each of them repeated an arbitrary number of times, e.g.
B=[1;2;3;3;3;4;5;5;6;7];
I want to obtain a column vector C reporting the elements of B with row coordinates equal to the row coordinates of each natural number last repetition in A. In the example:
C=[B(2);B(5); B(6); B(10)];

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采纳的回答

Andrei Bobrov
Andrei Bobrov 2013-11-28
[ii,ii]=unique(A,'last');
C = B(ii);

更多回答（1 个）

Roger Stafford
Roger Stafford 2013-11-28
C = B(find([diff(A)~=0,true]));
Note that for this to work, B should have at least as many elements as A.

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