# In regard to contour error

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bryan Kim on 15 Oct 2015
Answered: Martin Schätz on 15 Oct 2015
x=25:50;
nx=length(x)
y=25:50;
ny=length(y)
h=1;
for i=25:50
for j=25:50
v(i,j)=0;
npbc(i,j)=0;
roh(i,j)=0;
perm(i,j)=8.854e-12;
end
end
for i=25:50
npbc(i,25)=2;
end
for j=25:50
npbc(i,1)=3;
end
for j=25:50
v(50,j)=0;
npbc(50,j)=1;
end
for i=25:50
v(i,50)=100;
npbc(i,50)=1;
end
v(50,50)=50;
npbc(50,50)=1;
k=0;
eps=1.e-07;
alpha=1.5;
reler=eps+1;
while reler>eps
k=k+1
vsum=0;
chgsum=0;
for i=25:50
for j=25:50
id=npbc(i,j);
if id ==1, continue, end
old=v(i,j);
switch id
case 0
v1=v(i-1,j);
v2=v(i+1,j);
v3=v(i,j-1);
v4=v(i,j+1);
case 2
v1=v(i+1,j);
v2=v(i+1,j);
v3=v(i,j-1);
v4=v(i,j+1);
case 3
v1=v(i-1,j);
v2=v(i+1,j);
v3=v(i,j+1);
v4=v(i,i+1);
otherwise
v1=v(i+1,j);
v2=v(i+1,j);
v3=v(i,j+1);
v4=v(i,j+1);
end
v(i,j)=(v1+v2+v3+v4+h*h*roh(i,j)/perm(i,j))/4;
chg=v(i,j)-old;
v(i,j)=old+alpha*chg;
chgsum=chgsum+abs(chg);
vsum=vsum+abs(v(i,j));
end
end
reler=chgsum/vsum;
end
%
contour(x,y,v,30)
xlabel('x')
ylabel('y')
Error using contour (line 81) The size of X must match the size of Z or the number of columns of Z.
Error in FDM_laplace_matlab11111 (line 75) contour(x,y,v,30)

Martin Schätz on 15 Oct 2015
Your size of v is 50x50, and you want to get element 51 (v2=v(i+1,j) and i=50). If you want to use code as that you have to change end of your for cycle to 49.
Also contour needs X Y and Z as 2D matrix. Check the contour help for examples.