Attempted to access x(402); index out of bounds because numel(x)=401.

I want to apply forward downstream scheme on a linear advection equation; this code was used in forward upstream scheme and I could not modify it to fit my application.

The error is caused by the "k+1" in line 18 of the code

dx = 0.05; dt = 0.01; C = 1; A1 = 1-C*dt/dx; A2 = C*dt/dx;
x = [0:dx:20];
N = length(x);
for k = 2:N
    if (x(k) >= 4) && (x(k) <= 6)
        u(k) = cos(0.5*pi*(x(k)-5));
    else
        u(k) = 0;
    end
end
u(1) = u(N);
for k = 1:N
    uplot(1,k) = u(k);
end
for iout = 1:5
    for n = 1:5
        for k = 2:N
            u1(k) = A1*u(k)+A2*u(k+1);
        end
        u1(1) = u1(N);
        for k = 1:N
            u(k) = u1(k);
        end
    end
    for k = 1:N
        uplot(iout+1,k) = u(k);
    end
end

Answer 1

[Stalin Samuel]

instead of N use N-1

[Hassan]

In which line?

[Stephen23]

Line 17: for k = 2:N-1.