Converting matrix entries satisfying a threshold condition.
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I have a matrix of numeric entries and wish to convert each entry above a specified threshold to one and all other entries to zero. This has to be an elegant way to do this without a "for" loop. Perhaps using the "find" command in some manner?
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Star Strider
2015-1-29
There are likely a number of ways.
One approach:
M = magic(6);
Mm = mean(M(:));
M(M>Mm) = 1;
M(M~=1) = 0;
It sets all the entries greater than the mean to 1, and then uses that result to set the rest to 0.
4 个评论
Image Analyst
2015-1-29
编辑：Image Analyst
2015-1-29
Or, instead of the last 3 lines:
M = M > someThreshold;
Tamir Eisenstein
2020-3-6
What if my threshold is not a specific number but a percentile? for example, set the top 20% values to 1 and the rest to 0.
Star Strider
2020-3-7
@Tamir Eisenstein —
M = randi(99, 10); % Create Matrix
Msort = sort(M(:),'descend'); % Sorted Vector
Threshold = Msort(fix(numel(M)*0.2)); % Find Top 20% Value
Out = zeros(size(M))~=0; % Create Logical Matrix
Out(M >= Threshold) = 1; % Desired Result
Zakaria Abdelli
2022-10-21
编辑：Zakaria Abdelli
2022-10-21
how do i do it with 3 and others 0 can you give me a hint pleas im just a newbee???
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