How to set a threshold based on the values of an array vector ?

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chocho
chocho 2017-5-7
评论： chocho 2017-5-7
hi experts, I want to set a threshold based on the percentage of values in an array vector(320*1), Thus the value with the highest percentage will be my threshold for future use.
I want to plot the histogram of this array while the Y-axis have the percentage of each value occured in the array vector.
Any help or an ideat about how to set a threshold, i really appreciate it !

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回答（1 个）

Image Analyst
Image Analyst 2017-5-7
Use the > operator:
aboveThresholdIndexes = yourSignal > someThresholdValue; % A logical vector.
% If you want to extract those points:
aboveThreshold = yourSignal(aboveThresholdIndexes);
I leave it up to you to computer someThresholdValue because we don't know exactly what "threshold based on the percentage of values in an array" means. Do you mean like a percentage of 320 (the number of values in the array), or do you somehow want to take into account the values of those elements, in which case cumsum() might help?
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Image Analyst
Image Analyst 2017-5-7
That's because you never defined someThresholdValue. If you need to determine it by looking at the histogram, then call the histogram function:
histogram(yourSignal);
Obviously, just like someThresholdValue, you need to replace yourSignal with the actual name of your variable, and of course you need to have defined it already.
chocho
chocho 2017-5-7
@Image Analyst Friend my goal is to define the threshold, how to define it and still don't know what's it. did you get it ?
Even histogram(yourSignal); is not working because of my array vector is of type double.

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