Parameter fitting using nlinfit (high order ODEs)
2 views (last 30 days)
Show older comments
I am trying to fit data on multi-dimensional ODEs:
function output = myfunc(pars,tspan)
% we just rename the variable here for use in the ODE
k = pars;
function dCadt = ode(t,Ca)
% this is the ODE we are fitting to
dCadt(1) = -k(1)*Ca(1);
dCadt(2) = k(2)*Ca(1)*Ca(2);
end
% Initial concs. of Ca.
Cao = [2 3]';
[t,Ca] = ode15s(@ode,tspan,Cao);
output = Ca;
end % myfunc
Calling function:
tspan = [0 0.1 0.2 0.4 0.8 1]';
Cadata = [2.0081 1.5512 1.1903 0.7160 0.2562 0.1495;
2.0081 1.5512 1.1903 0.7160 0.2562 0.1495]';
parguess = [1.3 2]; % nonlinear fits need initial guesses
[pars, resid, J] = nlinfit(tspan,Cadata,@myfunc,parguess)
However it always give this error:
Error using nlinfit (line 185)
Requires a vector second input argument.
When I run same program with lsqcurvefit, it runs smoothly!
Please anyone help me to sort this error!
0 Comments
Answers (1)
Star Strider
on 5 Sep 2014
That has to do with differences between lsqcurvefit (that will fit matrix dependent variables) and nlinfit that will only fit vector dependent variables.
4 Comments
Star Strider
on 6 Sep 2014
I don’t remember if nlparci will work when you’re fitting two dependent variables, since it’s been a while since I tried that. I believe it will, but I know nlpredci will not.
See Also
Categories
Find more on Ordinary Differential Equations in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!