maximum of elements

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Pieter
Pieter 2011-4-5
Hello,
I have a dataset 'a' with 2000 rows and 1 column. I want to create a new dataset 'b' which contains values that are the maximum of the 10 previous rows of 'a'. So row 11 of dataset 'b' has to contain the maximum value of rows 1-10 of dataset 'a' How can I program this?
Thanks, Pieter

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采纳的回答

Arnaud Miege
Arnaud Miege 2011-4-5
There may be a cleaner way of doing this the following should work:
b = zeros(size(a));
b(1:10) = a(1:10);
for k=11:length(a)
b(k) = max(a(k-10:k-1));
end
HTH,
Arnaud
  1 个评论
Pieter
Pieter 2011-4-5
Thanks!
Exactly what I was searching for!
Pieter

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更多回答（2 个）

Jan
Jan 2011-4-5
NLFILTER of Matlab's Image Processing Toolbox can calculate the moving max:
fun = @(x) max(x(:));
b = nlfilter(a, [10, 1], fun);
Do you have the Image Processing Toolbox?
  1 个评论
Jan
Jan 2011-4-5
Do not use this! It is more than 1000 times slower than the BUFFER method of my other answer.

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Jan
Jan 2011-4-5
If your input is not too large (2000 is no problem), you can expand the data using BUFFER. This is 1300 times faster than NLFILTER and much faster than the loop:
M = max(buffer(a, 10, 9, 'nodelay'))
M = M(:); % BUFFER replies a row vector
b = [a(1:10); M(1:end - 1)];

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