RE: Map the chi2

Great! It works!

Thanks a lot!!!

Bye...

> -----Original Message-----
> From: Rene Brun [mailto:Rene.Brun_at_cern.ch]
> Sent: Tuesday, March 11, 2008 09:58
> To: Manuel Mussini
> Cc: 'Lorenzo Moneta'; roottalk_at_lxbuild091.cern.ch
> Subject: Re: [ROOT] Map the chi2
>
> What you show is OK for scanning 2 parameters. However replace
>
> scan01->SetBinContent(p0, p1, calcChi2);
>
> by
>
> scan01->Fill(p0, p1, calcChi2);
>
>
> You can specify a null pointer for the send argument of Eval.
>
> Rene
>
> Manuel Mussini wrote:
> >
> > Hi Rene,
> >
> > you mean something like this?
> >
> > TH2D *scan01 = new TH2D("scan01", "Scan par[1] vs par[0]", 17, 0.235,
> > 0.405, 36, 2.45, 6.05);
> >
> > Double_t p0p1p2[3] = {0., 0., cdfCrossSectionFit->GetParameter(2)};
> >
> > Double_t calcChi2 = 0;
> >
> > for (Double_t p0 = 0.24; p0 <= 0.41; p0 += 0.01)
> >
> > {
> >
> > p0p1p2[0] = p0;
> >
> > for (Double_t p1 = 2.5; p1 <= 6.; p1 += 0.1)
> >
> > {
> >
> > p0p1p2[1] = p1;
> >
> > gMinuit->Eval(0, ???, calcChi2, p0p1p2, 3);
> >
> > scan01->SetBinContent(p0, p1, calcChi2);
> >
> > }
> >
> > }
> >
> > scan01->Draw("SURF2");
> >
> > Where can I get the second argument for Eval?
> >
> > Bye...
> >
> > > -----Original Message-----
> >
> > > From: Rene Brun [mailto:Rene.Brun_at_cern.ch]
> >
> > > Sent: Tuesday, March 11, 2008 08:37
> >
> > > To: Manuel Mussini
> >
> > > Cc: 'Lorenzo Moneta'; roottalk_at_lxbuild091.cern.ch
> >
> > > Subject: Re: [ROOT] Map the chi2
> >
> > >
> >
> > > Hi Manuel,
> >
> > >
> >
> > > What you require should be quite easy using:
> >
> > > gMinuit->Eval(Int_t npar, Double_t *grad, Double_t &fval, Double_t *par,
> >
> > > Int_t flag);
> >
> > >
> >
> > > Create a TH3 (or TGraph2D), make your nested 3 loops on each parameter
> >
> > > in the limits you want.
> >
> > > In the loop call gMinuit->Eval and store the returned value fval in your
> >
> > > TH3 or TGraph2D.
> >
> > >
> >
> > > Rene Brun
> >
> > >
> >
> > > Manuel Mussini wrote:
> >
> > > > Hi Lorenzo,
> >
> > > > contours scans only "near" the found minimum so I think it isn't
> > the right
> >
> > > > choice for searching for another eventual "far" minimum!
> >
> > > > I've never tried SCAN! I'll do it as my next step!
> >
> > > > Is it possible to scan "by hand"? I mean ... can I fix all my 3
> > parameters
> >
> > > and
> >
> > > > evaluate the chi2? With TMinuit::FixParameter(Int_t) I think I can
> > get the
> >
> > > first
> >
> > > > part but ... how to update the chi2?
> >
> > > > The best result would be to obtain a 3D histo showing the chi2
> > surface (for
> >
> > > each
> >
> > > > parameters couple)!
> >
> > > >
> >
> > > >
> >
> > > > Bye.
> >
> > > >
> >
> > > >
> >
> > > >
> >
> > > > ________________________________________
> >
> > > > From: Lorenzo Moneta [mailto:Lorenzo.Moneta_at_cern.ch]
> >
> > > > Sent: Monday, March 10, 2008 23:14
> >
> > > > To: Manuel Mussini
> >
> > > > Cc: roottalk_at_lxbuild091.cern.ch
> >
> > > > Subject: Re: [ROOT] Map the chi2
> >
> > > >
> >
> > > > Hi Manuel,
> >
> > > >
> >
> > > > you can either scan a single parameter around the minimum, (command
> > SCAN in
> >
> > > > Minuit) or build contours for two parameters, like in fitcont.C.
> >
> > > > I think contours will give you the best way for maping the chi2
> > around the
> >
> > > > minimum.
> >
> > > >
> >
> > > > Cheers
> >
> > > >
> >
> > > > Lorenzo
> >
> > > > On Mar 10, 2008, at 7:20 PM, Manuel Mussini wrote:
> >
> > > >
> >
> > > >
> >
> > > > Hi,
> >
> > > > I have a TH1D and a 3 parameters user defined TF1 to fit it.
> >
> > > > Which is the best way to map the chi2 around the convergence point?
> >
> > > > I thoughed to map the 3 parameters in pairs (fix one of them and
> > scan the
> >
> > > other
> >
> > > > two) but it not so clear (to me!) how to implement the mapping!
> >
> > > > I've tried the fitcont.C tutorial but this is not what I want!
> >
> > > >
> >
> > > > Thanks!!!
> >
> > > >
> >
> > > > Bye.
> >
> > > >
> >
> > > >
> >
> > > >
> >
Received on Tue Mar 11 2008 - 10:03:09 CET