Index in position 2 exceeds array bounds (must not exceed 50).

code:

function main
% solution of 2D elliptical solution
% using Line Over Relaxation Method(LSOR)
% ep is accepted error
%Tridiag: Tridiagonal equation solver banded system
%stream function solver for inlet aswell as for outlet with Dirichlet
%conditions
clc;
clear all;
eps = 0.001;
omega = input(' enter the omega value: ');
beta = input (' enter the beta value: ');
n= 100000;
nx = 51;
ny = 51;
T(1:nx, 1:ny-1) = 0;
TN(1:nx, 1:ny-1) = 0;
T(13:nx, 1)= 100;
T(nx, 1:31) = 100;
TN(13:nx, 1)= 100;
TN(nx, 1:31) = 100;
% its number of iteration
coeff = ( 2*(1+beta^2));
for iterations = 1:n
    for j = 2:ny-1
        a(1:nx-2) = -coeff;
        b(1:nx-2)=  omega;
        c(1:nx-2)= omega;
        for i = 2:nx-1 
            r(i-1) = - coeff*(1-omega)*T(i,j)-omega*beta^2*T(i,j+1)-omega*beta^2*TN(i,j-1);
        end
        r(1)= r(1)-omega*TN(1,j);
        r(nx-2)= r(nx-2)-omega*TN(nx,j);
        y = Tridiagonal(c,a,b,r);
        for k = 1:nx-2
            TN(k+1,j)= y(k); 
        end
    end
    error = abs(TN-T);
    totalerror = sum(error,'all');
    if totalerror <= eps
        break
    end
    T=TN;
end
iterations
contour(TN');
end

result:

enter the omega value: 1.2

enter the beta value: 1

Index in position 2 exceeds array bounds (must not exceed 50).

Error in sf1 (line 30)

r(i-1) = - coeff*(1-omega)*T(i,j)-omega*beta^2*T(i,j+1)-omega*beta^2*TN(i,j-1);

Answer 1

[Walter Roberson]

ny = 51;
T(1:nx, 1:ny-1) = 0;

You initialize 51-1 = 50 columns in T

for j = 2:ny-1

j will be as much as 51-1 = 50

r(i-1) = - coeff*(1-omega)*T(i,j)-omega*beta^2*T(i,j+1)-omega*beta^2*TN(i,j-1);

When j becomes 50, then j+1 becomes 51, and T(2,51) would be asked for, but column 51 of T has not been initialized

[Aman Murkar]

thanks I got it . Its my mistake there should be T(1:nx, 1;ny) by mistake i wrote 1:ny-1.

Thanks for response