MATLAB: How to declare and iterate a variable in an ODE driver file

functionMATLABodescript

I have a pair of function and ode driver files. Currently, all values except initial conditions are declared as variables in the function file.
I would like to iterate on one variable, and check if the result is better than the previous value.
For example,
  1. start with Snh_in_1=1,
  2. run the ODE,
  3. print y(end,3).
  4. +0.1 to Ssnh (i.e. Snh_in_1 = 1.1)
  5. run the ODE,
  6. print new y(end,3).
  7. if new y(end,3), > original y(end, 3), repeat from step 1.
  8. stop when new y(end,3) less than or equal to previous y(end,3), and report this value of Snh_in_1.
These are my code so far
Function file: https://pastebin.com/Mp43ea1v
Driver file: https://pastebin.com/ct8iNL8W
I can imagine an if loop that might work:
result2 = 2;
result1 = 1;
Ssnh_in_1 =  1;
if result2 >= result1
    [t,y]=ode15s(@pha_cont,[0,15],y0);
    result1 = y(end,3);
    Ssnh_in_1 = Ssnh_in_1 + 0.1;
    [t,y]=ode15s(@pha_cont,[0,15],y0);
    result2 = y(end,3);
else
    disp(Ssnh_in_1)
end
But I have no idea how to pass this variable from the driver into the function file.
How can I do what I want in Matlab? Thanks in advance!

Best Answer

yold = -Inf;
Ssnh_in_1 =  1;
[t,y]=ode15s(@(t,y)pha_cont(t,y,Ssnh_in_1),[0,15],y0);
ynew = y(end,3);
while yold < ynew
 Ssnh_in_1 = Ssnh_in_1 + 0.1;
 [t,y]=ode15s(@(t,y)pha_cont(t,y,Ssnh_in_1),[0,15],y0);
 yold = ynew;
 ynew = y(end,3);
end
disp(Ssnh_in_1)
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