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How to remove repeated neighbour numbers?

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Amin Gan
Amin Gan on 13 Nov 2015
Commented: Amin Gan on 13 Nov 2015
I have two A and B vectors, for example:
A=[9 9 8 7 6 6 6 7 9 9 10 9]
B=[1 1 2 3 1 2 3 2 3 2 4 5]
I want to keep only one number of each repeated value from A, and then make an average value from B.
At the end I want to get this:
Anew=[9 8 7 6 7 9 10 9]
Bnew=[1 2 3 2 2 2.5 4 5]
I do not want to lose the second/third 9 or second 7 of A.I just want to remove the repeated neighbour(s) value from A (with N numbers) and make an average of B.
Thank you

Accepted Answer

arich82
arich82 on 13 Nov 2015
Edited: arich82 on 13 Nov 2015
We can construct a mask to get the non-repeated elements of A. Then, cumsum(mask) will effectively give a phase number for each "new" (i.e. non-repeated) entry in A, which we can use to accumulate B:
A=[9 9 8 7 6 6 6 7 9 9 10 9]
B=[1 1 2 3 1 2 3 2 3 2 4 5]
mask = [true, diff(A) ~= 0];
Anew = A(mask)
Bnew = accumarray(cumsum(mask).', B, [], @mean).'
output:
Anew =
9 8 7 6 7 9 10 9
Bnew =
1.0000 2.0000 3.0000 2.0000 2.0000 2.5000 4.0000 5.0000
Please accept this answer if it helps, or let me know in the comments if I've missed something.

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