System of ODE - part III

[Dennis Bayrock]

Hello!

   I want to thank everyone again in helping me (particularly Przemek 
Klosowski!) in helping me to understand Octave's syntax. I am very 
grateful. With some decifering, I have managed to properly enter my own 
model consisting of a system of differential-algebraic equations into 
Octave in order for it to integrate the equations. I am happy to report 
that it works very well! The results with initial test parameters are 
precisely what was expected!

   Now,  is there a way to have Octave determine values for multiple 
initial constants that are part of my model so that a value from one of 
the integrated equations can match a specified value? Basically I want 
to curve fit the resulting plots to my actual experimental data and have 
Octave determine the best values for the constants that would accomplish 
this. In the past I have used Excel's SOLVER function to accomplish this 
task but wish to know if Octave can do the same thing.
   Again I would humbly ask that someone would give me an actual 
example that I could enter into Octave so that I can learn by example. 
As I mentioned before I am not an engineer or a mathematician but would 
like to learn more about the mathematics in this area of research.

   If a hypothetical example would be of use as a base, then:


function res = f (x, xdot, t)
                D=0.02
                umax=0.4
         res = zeros (3,1);
         res(1) = xdot(1) - D*x(1)*x(2)*xdot(3);
         res(2) = xdot(2) - umax*x(1)*x(3)*xdot(1);
         res(3) = xdot(3) - x(1) - D*xdot(1) - xdot(2);
endfunction

x0 = [5,50,0]; 
xdot0 = [0,0,0];

t = linspace (0, 100, 1000);
x = dassl ("f",x0,xdot0,t);
plot (t,x)
pause


   Thanks all in advance!

       Dennis Bayrock, P.hD 





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