# storing points using a threshold critera

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shobhit mehrotra 2014 年 8 月 20 日
コメント済み: Image Analyst 2014 年 8 月 20 日
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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### 回答 (1 件)

Image Analyst 2014 年 8 月 20 日

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?
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Image Analyst 2014 年 8 月 20 日
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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