finding the mean for large data

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FIR
FIR 2012-11-30
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
please help
for each 3x9 i want to perform
  2 个评论
Jos (10584)
Jos (10584) 2012-11-30
192 is not divisible by 9, so what to do with the last columns?
Image Analyst
Image Analyst 2012-11-30
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)

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回答（2 个）

Andrei Bobrov
Andrei Bobrov 2012-11-30
编辑：Andrei Bobrov 2012-11-30
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
Jan 2012-11-30
A = rand(3, 192);
B = reshape(A(:, 1:189), 3, 9, []);
C = squeeze(mean(B, 2));

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