In addition to Yannick answer, you may use the following :
{
Double_t par(np) ; // np = nbre of parameters
Double_t erpar(np) ; // the error vector
Int_t i ;
fct = new TF1("xxx",txt, fmin, fmax); //xxx = fonction
fct->GetParameters(par); // extract the param. values
chi2 = fct->GetChisquare() ; // extract the chi2
for (i=0 ; i < np; i++) // extract the param. error values
fct->GetParameters(&erpar[i]);
}
Let me know if you need something else about this topic.
Faouzi
F. Attallah
GSI mbH
Planckstr 1
D-64291 Darmstadt
Tel: +49 (0)6159 71 2743
Fax: +49 (0)6159 71 2901
Email: F.Attallah@gsi.de
On Mon, 5 Jul 1999, Patois Yannick wrote:
> Hello,
>
> You can have a look on the exemple "multifit.C"
> http://root.cern.ch/root/html/examples/multifit.C.html
>
> Look at the lines :
>
> g1->GetParameters(&par[0]);
> g2->GetParameters(&par[3]);
> g3->GetParameters(&par[6]);
>
> look at GetParameter and GetParameters in
> http://root..cern.ch/root/html/TFormula.h.
>
> Double_t TFormula::GetParameter(Int_t ipar) will let you get one
> parameter, eg :
> Double_t mean = fit->GetParameter(1);
>
> And void GetParameters(Double_t* params) will gives you every parameter in
> an array.
>
> Hope it helps,
>
> Yannick
>
> _/ Yannick Patois \_________________ Address (home) __________________
> | irc(undernet): Garp on #france25+ | La Villa des Sciences |
> | email : patois@ganil.fr | 12, avenue de Cambridge |
> | web :http://www.sura.org/~patois/ | 14200 Herouville-Saint-Clair |
> | Tel(home) :+33 02 31 94 50 32 | FRANCE |
> |___________________________________|__________________________________|
>
> On Mon, 5 Jul 1999, Stephen Markacs wrote:
>
> >
> > How do I get the mean and sigma from a fit? I know it prints them to the
> > root session, but I want to actually get at them within my code so I can
> > put them on my plot.
> >
> > Thanks.
> >
> > S t e p h e n M a r k a c s
> > stephen@phys.columbia.edu
> > http://phys.columbia.edu/~stephen/
> >
> >
>
>
>