Averaging every n elements of a vector in matlab

Question

I would like to average every 3 values of an vector in Matlab, and then assign the average to the elements that produced it.

Examples:

x=[1:12];
y=%T         


        

Answer 1

I would go this way:

Reshape the vector so that it is a 3×x matrix:

x=[1:12];
xx=reshape(x,3,[]);
% xx is now [1 4 7 10; 2 5 8 11; 3 6 9 12]

after that

yy = sum(xx,1)./size(xx,1)

and now

y = reshape(repmat(yy, size(xx,1),1),1,[])

produces exactly your wanted result.

Your parameter 3, denoting the number of values, is only used at one place and can easily be modified if needed.

Answer 2

You may find the mean of each trio using:

x = 1:12;
m = mean(reshape(x, 3, []));

To duplicate the mean and reshape to match the original vector size, use:

y = m(ones(3,1), :) % duplicates row vector 3 times
y = y(:)'; % vector representation of array using linear indices