How to store each iteration of a loop as it's own varible.

My current code keeps returning this error message...

Error in indexing (line 936)

R_tilde = builtin('subsref',L_tilde,Idx);

I'm trying to find a way that I can create the interior node equations for a heat transfer problem without having to hard code each equation because 8 nodes isn't so bad to code but 100 would be very cumbersome. Any help here would be greatly appreciated. This is the code I have right now and can't seem to figure out how to create this loop.

clear

close all

clc

format short

syms k h g_dot T_inf L delta_x %symbolic varibles.

T = sym('t',[8,1]);

EQ = sym('eqn',[8,1]);

n = 8;

for i = n-(n-1):1:n

EQ(i) = T(i-1) - 2*T(i) + T(i+1) == -2.8409

end

[Steven Lord]

Please show the full and exact text of the error message (all the text displayed in red in the Command Window) as that exact text may be useful in determining what's going on and how to avoid the error.

[Greg]

Error in indexing (line 936)

R_tilde = builtin('subsref',L_tilde,Idx);

Error in practice (line 18)

EQ(i) = T(i-1) - 2*T(i) + T(i+1) == -2.8409

Thats the exact message I get back.

Answer 1

[Chunru]

syms k h g_dot T_inf L delta_x  %symbolic varibles.
T = sym('t',[8,1]);
EQ = sym('eqn',[8,1]);
n = 8;
%for i = n-(n-1):1:n
% if i is from 1 to n as give above, you need to define T(0) and T(n+1).

% The following will defind the eq from i=2 to n-1.  You can manully define
% EQ(1) and EQ(n)
for i = 2:1:n-1
    EQ(i) = T(i-1) - 2*T(i) + T(i+1) == -2.8409;
end
EQ

EQ = 

[Greg]

Thank you so much! That did the trick!