# Permute a vector by a specific ordering

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David on 15 Jul 2014
Edited: Azzi Abdelmalek on 15 Jul 2014
I have two vectors of the same length x and y, and each value in y corresponds to its value in x by the same index number, e.g.
x=[1 3 2 5 4]
y=[.2 .6 .5 .4 .3]
form the ordered pairs (1, 0.2), (3, 0.6), etc. Now I'd like to sort the vector x, but want to preserve the relationship of the two vectors. One thing I tried but didn't work is
[X I]=sort(x)
Y=permute(y,I) % how to permute y by ordering given by I?
This doesn't change the ordering of y at all. For this example the answer should be
X=[1 2 3 4 5]
Y=[.2 .5 .6 .3 .4]
Any ideas?

Azzi Abdelmalek on 15 Jul 2014
Edited: Azzi Abdelmalek on 15 Jul 2014
x=[1 3 2 5 4]
y=[.2 .6 .5 .4 .3]
[X I]=sort(x)
Y=y(I)

Ben11 on 15 Jul 2014
You're almost there!
Try this:
[a b] = sort(x)
y = y(b)
y =
0.2000 0.5000 0.6000 0.3000 0.4000

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