MATLAB: How to use accumarray

for loopMATLABmean

I have a matrix of y=[9, 5346]
I want to find the the mean of every six values of each row. I tried this function but can't really figure out how to do it
 for ii=1:9
 oo(ii)=accumarray(1:6:5346,y(ii,:),,[],@mean);
   end
it's saying there is error in this code . I don't really know how this accumarray works.
Any help is appreciated

Best Answer

accumarray() can be a bit tricky to learn. I think this solves your problem. I commented it to help you see what is happening.
A = rand(9,5346); % Make up some fake data that is the same size as yours
At = A'; % Take the transpose, because accumarray works down columns.
numberPerGroup = 6;
numberGroups = 5346/6; % 931, but wanted you to see where this comes from
% The subs array indicates which rows (of the transposed array) are going to get grouped. You have 931 groups total, each gather 6 rows.
subs = repmat(1:numberGroups,[numberPerGroup,1]);
subs = subs(:);
% Preallocate the output array
output = zeros(numberGroups,9);
% Accumulate each column in turn
for nr = 1:9
    output(:,nr) = accumarray(subs,At(:,nr),[],@mean);
end
% Transpose the output back
output = output';
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