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## System of ODE - part III

**From**: |
Dennis Bayrock |

**Subject**: |
System of ODE - part III |

**Date**: |
Tue, 02 Oct 2001 19:05:34 -0600 |

**User-agent**: |
Mozilla/5.0 (Windows; U; WinNT4.0; en-US; rv:0.9.4) Gecko/20010913 |

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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**System of ODE - part III**,
*Dennis Bayrock* **<=**