How I can extract data from a vector based on index

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Rita
Rita 2016-6-3
回答： Stephen23 2022-4-11
I have an index and a vector I would like to have data from the vector which is not in the index!For example
A=[5 3 7 8 89 6]
index=[2 3 4 5]
Now I want to have B as my answer B=[5 6] Thanks!

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采纳的回答

Roger Stafford
Roger Stafford 2016-6-3
编辑：Roger Stafford 2016-6-3
B = A(setdiff((1:length(A)).’,index(:)));
or if you're sure A and index are row vectors just
B = A(setdiff(1:length(A),index));

更多回答（2 个）

Stephen23
Stephen23 2022-4-11
Ran in:
A simple and efficient approach:
A = [5,3,7,8,89,6];
index = [2,3,4,5];
B = A;
B(index) = []
B = 1×2
5 6
Johanna
Johanna 2022-2-21
I looking for the opposite command of setdiff. That is, taking the example from above, I want the answer to be B=[3 7 8 89].
In particular I'm actually looking for the mean of the values mentioned in my index vector. I tried mean(A(index)), however, this does not work.
I guess it has to be something like mean(A(setequal(1:length(A),index))), however, setequal does not exist. Thanks!

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