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Find the threshold point in a matrix

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MByk
MByk 2017 年 11 月 22 日
Commented: MByk 2017 年 11 月 23 日
I have a 178x13 double matrix. In each column there is a point where each data value starts to stay same. I want to find them (row number). For example for the first column it is 70. I tried "find(diff(values(:,1)) == 0, 1, 'first')" but it is not working. How can I do this? Thanks for the help.

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Image Analyst
Image Analyst 2017 年 11 月 22 日
You can have differences equal to zero that are not in the last stretch of zeros. Therefore you need to use findgroups() or regionprops() to find the first element of the last group of zeros. If you need a demo, attach your data in an mat file with the paper clip icon.

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MByk
MByk 2017 年 11 月 23 日
I saved the matrix as a txt file.
Image Analyst
Image Analyst 2017 年 11 月 23 日
That's not a great example because all those columns go steady state at exactly the same row. This simple code will do it quickly:
data = importdata('myfile.txt')
[rows, columns] = size(data)
for col = 1 : columns
fprintf('Finding where column #%d equals %f . . . ', col, data(end, col));
steadyStateLocations(col) = find(data(:, col) ~= data(end, col), 1, 'last');
fprintf('it happens at row %d.\n', steadyStateLocations(col));
end
MByk
MByk 2017 年 11 月 23 日
Thank you very much.

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