Area between two curves

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Christian Reece
Christian Reece 2015 年 4 月 23 日
回答済み: Star Strider 2015 年 4 月 23 日
I was wondering if there was a simpler/faster way of calculating the area between the two curves at each point (both of which are normailsed so the total area is 1). I am currently using a simple for loop to get the area between each set of points for the two curves, then subtracting it to get the difference i.e.
for i = 1:length(normpeak)-1
resN(i) = trapz(time(i:i+1),peak1(i:i+1));
resF(i) = trapz(time(i:i+1),peak2(i:i+1));
end
res = resN-resF;
This works, but unfortunately it is very slow. I was reading up on the trapz function and from what I understood it calculates the total integral by performing something very similar to what i'm doing now (see image) but sums the data at the end.
Is there a way to stop trapz from performing this summing of the data, so I can speed up my code?

採用された回答

Star Strider
Star Strider 2015 年 4 月 23 日
Use the cumtrapz function to get the cumulative integral at every point.
I don’t have your data so I can’t test it, but this approach could work:
res = cumtrapz(time, peak1) - cumtrapz(time, peak2);

その他の回答 (1 件)

Binbin Qi
Binbin Qi 2015 年 4 月 23 日
if you can get the points of every curve, you can use polyarea function to get the area, and then diff
  1 件のコメント
Christian Reece
Christian Reece 2015 年 4 月 23 日
Thanks for the answer, but this doesn't seem to work. I think I was too vague before but what I need is the difference in area at each point on the curve.

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