# Replace some values of a vector with another vector which has a different size

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Christina on 29 Apr 2015
Commented: Stephen23 on 29 Apr 2015
Hello
I've got the vector: source = [ 0 0 1 0 1]
and the vector a = [2 3],
which has a different size to source.
I'd like to replace in the source vector the elements that are equal to 1, with those of vector a.
The final vector b should be: b = [0 0 2 0 3]
Any thoughts on this?
Thank you!

Thorsten on 29 Apr 2015
Edited: Thorsten on 29 Apr 2015
source(source == 1) = a
Christina on 29 Apr 2015
Thank you! It works!
pfb on 29 Apr 2015
However, that changes "source" instead of creating "b", as asked in the question.

pfb on 29 Apr 2015
b=zeros(size(source));
b(find(source))=a;
of course this works only if the number of nonzero elements in source are the same as the elements in a.
Christina on 29 Apr 2015
Thank you! It works

Stephen23 on 29 Apr 2015
Edited: Stephen23 on 29 Apr 2015
This can be achieved very simply using basic logical indexing:
>> A = [ 0 0 1 0 1];
>> B = [ 2 3];
>> A(A==1) = B
A = 0 0 2 0 3
On my computer this was almost twice as fast compared to using find and zeros.
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James Tursa on 29 Apr 2015
Stephen switched nomenclature. His starting "A" is your "source" his "B" is your "a", and his resulting "A" is your "b".
Stephen23 on 29 Apr 2015
Guilty as charged.