# Getting error: Error using .* Matrix dimensions must agree. Please help. The code the given below.

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Shashank on 2 Dec 2012
Nx = 100;
Ny = 20;
Nt = 400;
x = 0:10/Nx:10;
y = -1:2/Ny:1;
t = 0:1/Nt:1;
Dx = 10/Nx; % delta x
Dy = 2/Ny; % delta y
Dt = 1/Nt; % delta t
%%Numerical Solution using alpha (a) = 1
% Constants
a = 1.0; % alpha
Xd = a*Dt/(Dx^2); % Diffusion Length Scale in x
Yd = a*Dt/(Dy^2); % Diffusion Length Scale in y
c = Dt/(2*Dx); % Convection Length Scale
% Boundary Conditions
T = zeros(Ny+1,Nx+1,Nt+1); % Scalar field
T(1,1:end,:) = 0; % Bottom Wall
for m = 1:Ny+1
T(m,1,:) = (1 - (y(m).*y(m))).^2; % Inlet
end
% Forward Euler in Time, Central Differencing in Space
maxiter = 500;
for k = 1:maxiter
Tlast = T; % saving the last guess
T(:,:,1) = Tlast(:,:,end); % initialize the scalar field at t = 0 to the last guess
for i = 2:Nt+1
T(2:end-1,2:end-1,i) = (1-(2*Xd)-(2*Yd))*T(2:end-1,2:end-1,i-1) + (Xd-((3/2)*c*(1-(y(2:end-1).^2)))).*T(2:end-1,3:end,i-1) + (Xd+((3/2)*c*(1-(y(2:end-1).^2)))).*T(2:end-1,1:end-2,i-1) + Yd*T(3:end,2:end-1,i-1) + Yd*T(1:end-2,2:end-1,i-1);
T(end,1:end,i) = (4*T(end-1,1:end,i) - T(end-2,1:end,i))/3; % Top Wall (dT/dy = 0)
T(1:end,end,i) = (4*T(1:end,end-1,i) - T(1:end,end-2,i))/3; % Outlet (dT/dx = 0)
end
err(k) = max(abs(T(:)-Tlast(:))); % finding the residual value between two successive iterations
if err(k) < 1E-04
break; % stopping the solution is the residual value is small
end
end
Walter Roberson on 3 Dec 2012
The code here is close enough to the code in your other question that I would suspect siilar problems.