Axis problem in contour plotting

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John Doe 2019-7-30

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/474181-axis-problem-in-contour-plotting

评论： Star Strider 2019-8-1

采纳的回答： Star Strider

在 MATLAB Online 中打开

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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采纳的回答

Star Strider 2019-7-31

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/474181-axis-problem-in-contour-plotting#answer_385526

在 MATLAB Online 中打开

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')