Index exceeds the number of array elements (252).

% Explicit Quickest scheme

clc; clear all;

xmin = 0; % [m]

xmax = 50*1000; % [m]

dx = 200; % [m]

tmax = 0.5*24*3600; % [s]

u = 0.45; % [m/s]

D=10; %[m2/s]

k=0.1/(24*3600); %[1/s]

dt = 50; % [s]

No = (xmax - xmin)/dx;

x = xmin : dx : xmax + dx;

%% initial and Boundary conditions

for i = 1:length(x)

if x(i)<=0

Co(i) = 100;

else

Co(i) = 0;

end

end

C = Co;

Cp = Co;

% Analytical solution

ns = tmax/dt;

for n = 1 : ns

for i = 1 : No+2

if x(i)<=u*tmax

d(i) = 100;

else

d(i) = 0;

end

end

end

% Quickest

ns = tmax/dt;

for n = 1 : ns

for i = 3 : No+2

F=D*dt/(dx)^2;

g=u*dt/dx;

gr= (C(i+1)-C(i))/dx;

gl=(C(i)-C(i-1))/dx;

cr=(C(i+1)-2*C(i)+C(i-1))/dx^2;

cl=(C(i-2)-2*C(i-1)+C(i))/dx^2;

Cp(i) = C(i)-g*((0.5*(C(i)+C(i+1))-0.5*dx*g*gr-0.166*dx^2*(1-g^2-3*F)*cr)-(0.5*(C(i-1)+C(i))-0.5*dx*g*gl-0.166*dx^2*(1-g^2-3*F)*cl))+F*((dx*gr-0.5*dx^2*g*cr)-(dx*gl-0.5*dx^2*g*cl))-k*C(i)*dt;

end

C = Cp;

end

[AC_GBX]

Hey ummabb66,

please use the code insert function to display your code, so it can be understood. What is you exact problem?

Answer 1

[Gautam]

Hello, ummaab66

The error id in the line with the expression

gr= (C(i+1)-C(i))/dx;

The array C has 252 elements and i goes from 3 to 252. So, when you try to access the element C(i+1) when i is 252, MATLAB is not able to find the element and throws the error.