How I can extract data from a vector based on index

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!

Answer 1

[Roger Stafford]

   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));

[Rita]

Thanks Roger

Answer 2

[Stephen23]

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

Answer 3

[Johanna]

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!

[Stephen23]

" I want the answer to be B=[3 7 8 89]."

A = [5,3,7,8,89,6];
index = [2,3,4,5];
B = A(index)

B = 1×4

3 7 8 89

https://www.mathworks.com/help/matlab/learn_matlab/array-indexing.html

[Janiece Jackson]

Thank you so much for this answer!!!