storing points using a threshold critera

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shobhit mehrotra
shobhit mehrotra 2014-8-20
评论： Image Analyst 2014-8-20
i have data of time vs concentration. i want to first find the point that crosses a threshold (concentration) of 15, then find the next point which goes below the threshold. then i want to store all of the points between the first point and second point into a vector in the workspace p(1), p(2) p(3) ... i want to create a loop such that it repeats finding the first and last points from time =0 to time = end. attached is a picture the points in yellow are the data that exceeds the threshold

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Image Analyst
Image Analyst 2014-8-20
编辑：Image Analyst 2014-8-20
OK. Seems easy enough. What did you try? Did you try
indexesAboveThreshold = find(signal > 15);
signalElementsAboveThreshold = signal(indexesAboveThreshold);
??? Do you actually have a question?
If you don't care about what the indexes are you can do it in a single line:
signalElementsAboveThreshold = signal(signal > 15);
Did you try that? What happened when you did?
  2 个评论
shobhit mehrotra
shobhit mehrotra 2014-8-20
my question is how do i create a program that would take the first point above the threshold then find the next point that dips below the threshold. then take all of the points in between and store it as a vector
Image Analyst
Image Analyst 2014-8-20
OK - you need to know how to create programs. There's a faq answer for that: http://www.mathworks.com/matlabcentral/answers/8026-best-way-s-to-master-matlab
By the way, it seems I already did the program for you, vectorized, with a for loop. Good luck in learning MATLAB! If you write an alternate program and need help, come back here.

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