how do i use contour command for rectangular plate ?

dear friends,

i have one regtangular plate and when i use contour command i did not obtain the figure i want, could you please see where do i have mistake.

i am sharing also the figure i want to obtain

%%% Point Gauss Seidel (PGS) 

close all, clc
format short g

%Defining the constants
L=1;                                % length
H=2;                                % Height
deltax=0.05
deltay=0.05
Beta=deltax/deltay
Beta2=Beta^2
jn=H/deltay                         % Maximum number of grid points along y
im=L/deltax                         % Maximum number of grid points along x
T1=100; T2=0; T3=0; T4=0;           % boundary conditions
y=2:-deltay:0;
x=0:deltax:L;
% initialize T_old to the initial guess values
T_old=zeros(jn+1,im+1);
% set boundary conditions
T_old(1,1:im+1)=T1;
T_old(jn+1,1:im+1)=T3;
T_old(2:jn+1,1)=T2;
T_old(2:jn+1,im+1)=T4;
T_new = T_old;
Error = 0.011;  % could be any number that is greater than Errormax
Errormax=0.01;
t=0;

while Error > Errormax
    t=t+1;
    for i=2:jn 
        for j=2:im
            T_new(i,j)=(1/(2*(1+Beta2)))* (T_new(i-1,j)+T_new(i+1,j)+Beta2*(T_new(i,j+1)+T_new(i,j-1)) ) ;       
        end
    end
Error = sum(sum(abs(T_old-T_new),2))   ; 
T_old = T_new;

end
contour(T_new(2:en,:))

Answer 1

[Cris LaPierre]

Include your x and y vectors when plotting. You'll have to do some manipulation of y since you create it starting at 2 and decrement to 0. You can also specify the number of contour levels if you want that to match.

contour(X,Y,Z)

You'll also want to format the axes so they use the same spacing (axis equal)

%Defining the constants
L=1;                                % length
H=2;                                % Height
deltax=0.05;
deltay=0.05;
Beta=deltax/deltay;
Beta2=Beta^2;
jn=H/deltay;                         % Maximum number of grid points along y
im=L/deltax;                         % Maximum number of grid points along x
T1=100; T2=0; T3=0; T4=0;           % boundary conditions
y=2:-deltay:0;
x=0:deltax:L;
% initialize T_old to the initial guess values
T_old=zeros(jn+1,im+1);
% set boundary conditions
T_old(1,1:im+1)=T1;
T_old(jn+1,1:im+1)=T3;
T_old(2:jn+1,1)=T2;
T_old(2:jn+1,im+1)=T4;
T_new = T_old;
Error = 0.011;  % could be any number that is greater than Errormax
Errormax=0.01;
t=0;

while Error > Errormax
    t=t+1;
    for i=2:jn 
        for j=2:im
            T_new(i,j)=(1/(2*(1+Beta2)))* (T_new(i-1,j)+T_new(i+1,j)+Beta2*(T_new(i,j+1)+T_new(i,j-1)) ) ;       
        end
    end
Error = sum(sum(abs(T_old-T_new),2))   ; 
T_old = T_new;

end

%% create contour plot
contour(x,fliplr(y),T_new,17,'k')
xlabel('X')
ylabel('Y')
axis equal

[mehmet salihi]

thank you very much for your fast help,

could you please tell me if i do not specify the number of contour levels , is it going to choose the values of levels arbitrary.

without specifying the number, it is working also but what is the logic of the command in case if we do not specify.

[Cris LaPierre]

Levels is an optional input. When you do not specify the levels, the contour function chooses the levels automatically.

[mehmet salihi]

thank you very much