to find average value in a particular range of a matrix

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ramya raj
ramya raj 2011-9-19
hai
i am having a matrix with values of size 1*700 i have to find the avg value of first 1 to 100 ,avg value of 100 - 200 and so on upto 600 -700 is there any function to find the average of 1 -100 and 100 - 200, 200 - 300,300 - 400,400 - 500,500 - 600,600 - 700,

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回答（1 个）

Andrei Bobrov
Andrei Bobrov 2011-9-19
variant 1 for the intervals: 1:100, 101:200,...,601:700
out = mean(reshape(yourmtx,100,[]));
variant 2 for the intervals: 1:100, 101:200,...,601:700
out = blkproc(yourmtx,[1 100],@mean)
variant 3 for the intervals: 1:100, 100:200,...,600:700
idx = bsxfun(@plus,0:100,(0:100:600)')';
idx(1) = 1;
mv = yourmtx(idx);;
mv(1)=nan;
out = nanmean(mv);
variant 4 for the intervals: 1:100, 100:200,...,600:700
out = mean(reshape(yourmtx,100,[]));
out(2:end) = mean([yourmtx(100:100:600);out(2:end)]);
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Daniel
Daniel 2012-1-27
Hello andrei.
I am having more or less the same problem.
But I need to extract mean values within a certain range of a matrix. This range is given by each column's min and max value, and a step.
Basically I've done the next:
1. I have a 2x720 matrix with data, let's call it A.
2. I calculate a = max(A), b = min(A).
3. I apply the histcnd function (which counts frequency of values within certain edges or range).
4. The edges = {b(1):2:a(1),b(2):10:a(2)}, that is from min and max value of each column of A, with a certain step (2 and 10).
This returns an answer matrix, whose dimension depends on the steps given.
This matrix needs to be divised by certain factors, but then, I have to re-multiply it to the values of the first matrix A. The problem? Matrixs dimension do not fit to do so. The solution would be to obtain a new matrix from A, containing mean values within each column given range (the ones used on 'edges').
Is this posible?
Thanks a lot!

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