Integration over two variable dependent function

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Özgür Alaydin 2022-3-9

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https://ww2.mathworks.cn/matlabcentral/answers/1667634-integration-over-two-variable-dependent-function

评论： Özgür Alaydin 2022-3-11

Dear all,

I have function which generates 3d plot. I change the function to obtain data dependent on the two variables then function is giving zero except last term after integration.

The code is as given below. This is working as i want and giving the correct plot.

clear

Nx=50;

Ny=50;

Mx=20e-9;

My=20e-9;

x=linspace(-Mx/2,Mx/2,Nx);

y=linspace(-My/2,My/2,Ny);

[X,Y]=meshgrid(x,y);

Vb1=0.228;

Rx1=5e-9;

Ry1=5e-9;

alfa=0e-9; w=1E+12; T=2*pi/w;

idx=(X/Rx1).^2 + (Y/Ry1).^2 < 1;

V0=(idx)*0 + (1-idx)*Vb1;

surf(x*1e9,y*1e9,V0)

However when i change the code as given below, it is not working, making all rows 0 except last one.

How can i correct it?

clear

Nx=50;

Ny=50;

Mx=20e-9;

My=20e-9;

x=linspace(-Mx/2,Mx/2,Nx);

y=linspace(-My/2,My/2,Ny);

Vb1=0.228;

Rx1=5e-9;

Ry1=5e-9;

alfa=0e-9; w=1E+12; T=2*pi/w;

T = 1.0;

for i=numel(x)

for j = 1:numel(y)

fx =@(t) x(i) + alfa.*sin(w.*t);

idx=@(t) (fx(t)./Rx1).^2 + (y(j)/Ry1).^2 < 1;

Vb = @(t) idx(t).*0 + (1-idx(t)).*Vb1;

V0(i,j) = (1/T).*integral(Vb,0,T,'ArrayValued',true);

end

surf(x*1e9,y*1e9,V0)

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Torsten 2022-3-9

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I must admit that I don't understand the function you are trying to integrate.

This gives you a code to integrate your original problem. Is it that what you want in a t-dependent form somehow ?

Vb1 = 0.228;
Rx1 = 5e0;
Ry1 = 5e0;
idx = @(x,y)(x/Rx1).^2 + (y/Ry1).^2 < 1;
V0 = @(x,y) idx(x,y)*0 + (1-idx(x,y))*Vb1;
V = integral2(V0,-10,10,-10,10)