Hi Bob, Thanks for reporting this problem. Now fixed in the CVS head. Rene Brun On Tue, 18 Sep 2001, Bob Schaefer wrote: > Hello, > > I seemed to find 2 problems while using root to fit histograms. 1) Funny > behavior in fitting sums of functions when a landau function is involved, and > 2) Getting the SetOptFit to display the parameters as described. > > > 1) I tried fitting a sum ("total") of a landau function and an exponential > > TH1F *hist; > > // fitting functions > TF1 *exp1, *land, *total; > // fitting parameters > Double_t par[5]; > > land = new TF1("land", "landau(0)",20,800); > hist->Fit(land,"WQ0","",300,800); > hist->Fit(exp1,"WQ0+","",20,200); > > exp1 = new TF1("exp1","expo(0)", 20, 800); > > land->GetParameters(&par[0]); > exp1->GetParameters(&par[3]); > > total->SetParameters(&par[0]); > > total = new TF1("total","expo(3)+landau(0)", 20, 800); > hist->Fit(total,"WR"); > > This works fine unless I try to do the fitting with the exponential parameters > FIRST in the parameter list, i.e., > > land->GetParameters(&par[2]); > exp1->GetParameters(&par[0]); > > total->SetParameters(&par[0]); > total = new TF1("total","expo(0)+landau(2)", 20, 800); > hist->Fit(total,"WR"); > > In which case the fit fails, complaining that the ERROR MATRIX IS NOT POSITIVE > DEFINITE. > > > 2) Fit parameters not being displayed > > According to the documentation: > > gStyle->SetOptFit(0101); > > should print the names/values of the parameters AND the Chi-squared. It > does not print the chi-squared, although it does print the parameters. > > However, if I use > > gStyle->SetOptFit(10101); > > it prints both chi sq and the parameters?! > > Thanks, > Bob Schaefer > > > > > > Root 3.1/02 on LinuxPPC2000 running on a Mac G4 dual processor. > > > ---------------------------------------------------------- > Robert K. Schaefer Email: bob@milkyway.gsfc.nasa.gov > NASA/GSFC Code 664 Phone: 301-286-0878 > Greenbelt, MD 20771 FAX: 301-286-1629 > ---------------------------------------------------------- >
This archive was generated by hypermail 2b29 : Tue Jan 01 2002 - 17:51:00 MET