How do I find a min/max value within a defined range for each column of a matrix?

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Kim
Kim 2013-2-4
回答： Mohammadhassan safavi 2018-10-30
I am sure this is so simple but I can't work it out. I have a 513*86 array where the columns are the variables and the rows are the samples that represent a time series of EEG data sampled at 256 Hz. I want to find the maximum and minimum values between the 200th and 400th rows. I can't seem to make this work. Any help would be so appreciated! Thanks Kim

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Kim
Kim 2013-2-4
Thank you so much for such a quick answer! I tried your code but I still have one problem.
I forgot to mention (sorry) I need it's index too. The code that I was using for one row of data was:
[minval,minindex] = min(meandata(N4index:P6index)); Where meandata is a vector representing a time averaged data series. The indexes are just time points found with the 'find' function but are about 200 and 400. I tried this
a=data(N4index:P6index,:); % isolate the section of interest? [min1,minindex]=min(a(:))
This returns a row vector of columns data, but it is the same number? Am I missing something?
Thanks again Kim

更多回答（2 个）

Azzi Abdelmalek
Azzi Abdelmalek 2013-2-4
编辑：Azzi Abdelmalek 2013-2-4
x=rand(513,86);
a=x(200:400,:);
min1=min(a(:))
max1=max(a(:))
  1 个评论
Azzi Abdelmalek
Azzi Abdelmalek 2013-2-5
x=rand(513,86);
a=x(200:400,:);
[min1,idx1]=min(a(:))
[max1,idx2]=max(a(:))
[ii1,jj1]=ind2sub([200 86],idx1)
[ii2,jj2]=ind2sub([200 86],idx2)
ii1=ii1+200;
ii2=ii2+200;
disp([min1,ii1,jj1]);
disp([max1 ii2 jj2]);

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Mohammadhassan safavi
here is the code: X is original data set, A is subset within the range
range =L:U;
A = X(range);
[value index]=max(A);
org_index= range(index);

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