# conditional array extraction based on control array

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Ivan on 24 Jan 2013
I have the following problem:
For example, I have three arrays:
x = [1,2,3,4,5,6,7,8,9,10] and its corresponding y values: y = [21,43,77,54,38,24,99,64,77,33] and also a "control" array: c = [3,5,7,9]
Is it possible to somehow extract from 'y' only those entries that have corresponding entries in both 'x' and 'c' array and put them in for example 'z'? In this case z = [77,38,99,77]
Thanks.

Cedric on 24 Jan 2013
Edited: Cedric on 24 Jan 2013
For the second part of the question:
z = y(c) ;
What do you mean by "corresponding entries in x "? How do you define correspondence if x and y don't have the same number of elements?

Ivan on 24 Jan 2013
I mean that only if entry exists in both 'x' and 'c' for instance '3' does, then to copy in this case 77 form 'y' into 'z'.
Cedric on 24 Jan 2013
Ok, so you can achieve that with intersect, as mentioned by Eric, below.

Eric Sampson on 24 Jan 2013
If I understand your question correctly, try this:
z=y(intersect(x,c));