Area under curves with different length (trapz)

Question

mael thevenot 2018-9-17

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https://ww2.mathworks.cn/matlabcentral/answers/419383-area-under-curves-with-different-length-trapz

回答： Fabio Freschi 2019-12-4

Hi,

I'm trying to use the trapz command on MatLab R2015b.

I have 2 waves of data : y1(1x1036 double) and y2(1x9958 double) with different acquisition time, and I want to compare the area under both curves. But since the second wave have way more points I found a value much higher that did not make sense.

How can I do to tell the trapz function to take one value out of 10 for exemple? I've tried messing with the X parameter in

trapz(X, Y)

but I did not manage to make it work.

Thanks

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Fabio Freschi 2019-12-4

Do you know the x axis for both waves?

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Answer 1

Fabio Freschi 2019-12-4

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/419383-area-under-curves-with-different-length-trapz#answer_404757

If you have the x axes for both waves, it is pretty easy to use trapz:

N1 = 1036;
N2 = 9958;
% wave 1
x1 = linspace(0,2*pi,N1);
y1 = sin(x1);;
% wave 2
x2 = linspace(0,2*pi,N2);
y2 = sin(x2);
% integrals
I1 = trapz(x1,y1)
I2 = trapz(x2,y2)