How can I calculate the area between two curves in a specific section?

2 次查看(过去 30 天)
I have two curves which have several intersection points (see attachment). I want to calculate the green filled area in between two intersection points. It works to calculate and display the intersection points. However I am struggling to calculate just this specific (green filled) area with the trapz function since there always pops up following error message:
"Index in position 1 is invalid. Array indices must be positive integers or logical values."
[xj,yj] = polyxpoly(x,y1,x,y2); %calculate intersection points %y1 straight line %y2 mean
mapshow(xj,yj,'DisplayType','point','Marker','o');%show intersection points
A=[xj,yj];
for n=length(xj):-1:1
k=A(n,:);
k(:,2)=[];
l=A(n-1,:);
l(:,2)=[];
isec1= find(y2==l);
isec2= find(y2==k);
a = trapz(isec1:isec2,y1(isec1:isec2,1))-trapz(isec1:isec2 ,y2(isec1:isec2,1));
end

回答(1 个)

Priyanshu Mishra
Priyanshu Mishra 2020-1-31
Hi Daniel,
When n=1, n-1 goes to zero for which A(0,:) is an invalid index. The error you are getting is becuse of this only.

类别

Help CenterFile Exchange 中查找有关 Numerical Integration and Differentiation 的更多信息

产品


版本

R2019b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by