Axis problem in contour plotting
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I have plotted this equation by this :
clear all
close all
a=1000;
b=1000;
v0=100;
V=zeros(1000);
V(:,1000)=0;
V(:,1)=0;
V(1,:)=0;
V(1000,:)=100;
[X,Y]=meshgrid(0.01:0.01:10, 0.005:0.005:5);
for x=1:1000
for y=1:1000
sum=0;
for k=1:111
n=(2*k)-1;
s=((sin(n.*pi.*x./a)).*(sinh(n.*pi.*y./a)))./(n.*sinh(n.*pi.*(b./a)));
sum=sum+s;
end
V(x,y)=(4.*v0./pi).*sum; %here
end
end
figure
[C,h]=contourf(V);
clabel(C,h)
grid on;
axis('square')
The problem is after running I get this sort of plot:
I am supposed to get something like this :
If I swap V(x,y) with V(y,x) [commented in the code], then I get the right axis. What is happening? Are my x,y values getting interchanged or something? How to resolve this issue? Kindly help!
Thanks!
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Accepted Answer
Star Strider
on 31 Jul 2019
If you use the meshgrid outputs (with one additional argument, so one additional matrix) you get the result you want. It also avoids the loops and is likely much faster:
a=1000;
b=1000;
v0=100;
[X,Y,K]=meshgrid(1:1000, 1:1000, 1:111);
N = 2*K-1;
s = @(x,y,n) ((sin(n.*pi.*x./a)).*(sinh(n.*pi.*y./a)))./(n.*sinh(n.*pi.*(b./a)));
V = 4*v0/pi*sum(s(X,Y,N),3);
figure
[C,h]=contourf(V);
clabel(C,h)
grid on;
axis('square')
I won’t post the plot image here, because it is the one you are supposed to get, and posting it would be redundant.
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