# Index in position 4 exceeds array bounds (must not exceed 1).

2 views (last 30 days)
Junseob Kim on 23 Jan 2020
Commented: Walter Roberson on 23 Jan 2020
for j = 2:ny-1
for i = 2:nx-1
Ex(i,j,n,1) = 150; %initial guess
Ey(i,j,n,1) = 200; %initial guess
for g = 1:gfinal-1
M11(i,j,n,g) = (1/(4*dt))*(g1+g2+g3)+(eps/dt)*(1+(alpha/kai0)*(3*(Ex(i,j,n+1,g))^2+(Ey(i,j,n+1,g))^2)+S(i,j,n+1));
M22(i,j,n,g) = (1/(4*dt))*(g1+g2+g3)+(eps/dt)*(1+(alpha/kai0)*((Ex(i,j,n+1,g))^2+3*(Ey(i,j,n+1,g))^2)+S(i,j,n+1));
M12(i,j,n,g) = ((2*eps)/dt)*alpha*kai0*Ex(i,j,n+1,g)*Ey(i,j,n+1,g);
M21(i,j,n,g) = ((2*eps)/dt)*alpha*kai0*Ex(i,j,n+1,g)*Ey(i,j,n+1,g);
M(:,:) = ([M11(i,j,n,g),M12(i,j,n,g); M21(i,j,n,g),M22(i,j,n,g)]);
Minv(:,:) = inv([M11(i,j,n,g),M12(i,j,n,g); M21(i,j,n,g),M22(i,j,n,g)]);
Ex(:,:,n+1,g+1) = Ex(:,:,n+1,g)- Minv(1,1)*X(i,j,n,g) - Minv(1,2)*Y(i,j,n,g);
if (abs(X(i,j,n)) <= tol && abs(Y(i,j,n)) <= tol)
break;
end
Ex(i,j,n,g+1) = Ex(i,j,n);
end
end
end
Hello. I am trying to solve newton's method problem.
But there's an error after M11(i,j,n,g) line. 'Index in position 4 exceeds array bounds (must not exceed 1).'
Can you help me with that problem?
Thanks!

James Tursa on 23 Jan 2020
Do this at the command line:
dbstop if error
Then run your code. When the error appears the code will pause will all variables intact. Examine them to see what their actual dimensions are, and then backtrack in your code to figure out why they are not the size that you expect.
Junseob Kim on 23 Jan 2020
Thank you so much!

Walter Roberson on 23 Jan 2020
Edited: Walter Roberson on 23 Jan 2020
You define
Ex(i,j,n,1) = 150; %
but we have no reason to expect that on the line
M11(i,j,n,g) = (1/(4*dt))*(g1+g2+g3)+(eps/dt)*(1+(alpha/kai0)*(3*(Ex(i,j,n+1,g))^2+(Ey(i,j,n+1,g))^2)+S(i,j,n+1));
that
Ex(i,j,n+1,g)
exists -- in particular the n+1 is a problem.

Junseob Kim on 23 Jan 2020
I put Ex(i,j,n+1,1) instead of Ex(i,j,n,1). But there's still error.
Junseob Kim on 23 Jan 2020
Thanks you btw!!
Walter Roberson on 23 Jan 2020
You have the same issue for Ey except worse since you do not assign to Ey inside the loop and so are not growing Ey as you go.
You possibly also have problems accessing S.