# finding the mean for large data

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FIR on 30 Nov 2012
I have 3 rows ans 192 column,i want to find mean for each 9 columns in row wise,
for ex if i have rand(3,192)
taking 3x9 , i need mean in row wise so i will have 3x1 matrix after finding mean
for each 3x9 i want to perform
##### 2 CommentsShowHide 1 older comment
Image Analyst on 30 Nov 2012
It's not "large" either. Before I read it I thought that he was talking hundreds of millions of elements, not five hundred and something. (And there is a "bug" for the case of calculating the mean for large numbers of singles)

Andrei Bobrov on 30 Nov 2012
Edited: Andrei Bobrov on 30 Nov 2012
A = rand(3,192);
n = 9;
s = size(A);
out = squeeze(nanmean(reshape([A nan(s(1),mod(-s(2),n))],s(1),n,[]),2));
or
out = blockproc(A,[1 n],@(x)mean(x.data));
or
k = s(2) - rem(s(2),n);
out = [squeeze(mean( reshape(A(:,1:k),s(1),[]),2 )) , mean(A(:,k+1:end),2)];

Jan on 30 Nov 2012
A = rand(3, 192);
B = reshape(A(:, 1:189), 3, 9, []);
C = squeeze(mean(B, 2));

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