How can I use for-loop to implement variable parameters?

Dursman Mchabe (view profile)

on 13 Oct 2018
Latest activity Edited by Stephen Cobeldick

Stephen Cobeldick (view profile)

on 14 Oct 2018
Hi all, on the attached m-file I try to use for-loop to pass variable parameters, some how I get an error message that says:
Index exceeds the number of array elements (0).
Error in euler>odesfun (line 145)
CH = Parameter(1);
Error in euler (line 51)
y(i) = y0 + odesfun().*delta;
I followed the example given in this link:
but it seems like I make a mistake somewhere in the code.
function my_ode()
%main code
T0 = 293;
T1 = 300;
Tf2 = 293;
a = 0.2;
R = 1; % not defined in your code
C = 1; % not defined in your code
tchange = (T1-T0)/a;
for ii = 1:(tchange)+1
Tf(ii) = T0 + a*(ii-1);
d = (Tf(ii) - Tf2)/(R*C);
e = -2/(R*C);
% d and e need to be passed as parameters
[t,T] = ode45(@ode1,[0 336],293,[],[d,e]);
figure (1)
plot(t,T)
end
end
function dTdt = ode1(t,T,param)
d = param(1);
e = param(2);
dTdt = d - e*T;
end

Stephen Cobeldick (view profile)

on 14 Oct 2018
Edited by Stephen Cobeldick

Stephen Cobeldick (view profile)

on 14 Oct 2018

Following the advice of old questions and answers is not a good idea, because the syntax can change. To parametrize a function you should follow the advice in the MATLAB documentation for your installed MATLAB version. Here is the online help for the current version:
It does not mention using a fifth input argument. It states that " ode45 only works with functions that use two input arguments, t and y. However, you can pass in extra parameters by defining them outside the function and passing them in when you specify the function handle." It also gives a link to a page that describes several ways to do this:
You can simply use an anonymous function to parametrize the function:
T0 = 293;
T1 = 300;
Tf2 = 293;
a = 0.2;
R = 1;
C = 1;
tchange = (T1-T0)/a;
for ii = 1:tchange+1
Tf(ii) = T0 + a*(ii-1);
d = (Tf(ii) - Tf2)/(R*C);
e = -2/(R*C);
fun = @(t,T) d - e*T;
[t,T] = ode45(fun,[0,336],293);
figure()
plot(t,T)
end