MATLAB: How to calculate average of certain value in a matrix

mathematicsprogramming

Hello, My problem is about how to calculate the average of certain values in a large matrix. I know how to calculate the 1st average of the matrix with matlab, but for the other one I tried with a for loop but I didn't manage to solve the problem.
Example:
calculate the average of every 2 values of A
A=
1
2
3
4
5
6
7
8
Av1=1,5 WITH MATLAB Av1=sum(A(1:2;1),1)./2
Av2=3,5
Av3=5,5
Av4=7,5
I did the following loop but it doesn't work :
for i=1:3
for k=2:4
Av=sum(A(i*2+1:2*k,1),1)./2
end
end
Thank you in advance

Best Answer

Av = mean(A([1:2:end;2:2:end]));
or
Av = sum(A([1:2:end;2:2:end]))/2;
ADD
 n = 3;
 Av = accumarray(floor((n:numel(A)+n-1)/n)',A(:),[],@mean);
or
n=3;
p = reshape([A(:);nan(mod(-numel(A),n),1)],n,[]);
l = isnan(p);
p(l) = 0;
Av = sum(p)./sum(~l);
if rem(numel(A),n) == 0 , just:
Av = mean(reshape(A,n,[]));
if you have Image Processing Toolbox then
Av = blockproc(A,[1 n],@(x)mean(x.data));
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