area between two overlapping plots

Hi,

I have a plot that of two curves that overlap and want to calculate the area of overlap. The plot looks as below. The curves are from data set and are not fit to any equation. How you I calculate the area of the overlapping region ?

Thanks in advance.

Answer 1

[KL]

You could use trapz to calculate the area under the curve.

https://www.mathworks.com/help/matlab/ref/trapz.html

But before that you need to calculate the intersecting portion of the curves. Check this example with some dummy data,

 x1 = 0.01:0.01:1;
 y1 = [sin(pi*x1) zeros(1,20)];
 x2 = x1+0.2;
 y2 = [zeros(1,20) sin(pi*x1)];
 y_d = [y2(y2<y1) y1(y1<y2)]; 
 area_int  = trapz(y_d)
 %plots in case you want to visualize
 plot(y1)
 hold on
 plot(y2)
 plot(y_d,'k-o')

[Sahithya S Iyer]

Thanks :)

[Alexander Collins]

I noticed that for when I do this the overlap values very close to zero (where one curve is on the order of 10E-7) get reshuffled to the end of the array, causing the whole thing to get shifted out of alignment.

Is this a known thing? Any ideas?