[ROOT] fit with TGraph..

From: Antoni Munar (munar@fnal.gov)
Date: Wed Jan 17 2001 - 21:30:04 MET 

I am using ROOT version 2.24/04 on IRIX at CDF

When I fit a TGraph with a polinomial function of grade 1
I have problems retreiving the fitting parameters.

I do the follow:

    TGraph *emGr[24];
    TGraph *hadGr[24];
    ..................

    for(k1=0.................
	
    emGr[k1]= new TGraph(nentries,xetmp,yetmp);
    hadGr[k1]= new TGraph(nentries,xhadtmp,yhadtmp);
    //xetmp and yetmp are arrays
	
    emGr[k1]->Fit("pol1","Q","");
    hadGr[k1]->Fit("pol1","Q","");

    emf[k1] = emGr[k1]->GetFunction("pol1");
    if(emf[k1]!=0) 
      printf("p1: %f\n",emf[k1]->GetParameter(1));

my problem is that the pointer returned by GetFunction is always 0...

Any suggestion...

Thanks very much

**************************************************************
*    Antoni Munar Ara        	   munar@fnal.gov            *
*                                                            *
*    INFN Sezione di Pisa                                    *
*    Fermi National Laboratory     Phone:  (630)840-8426     *
*    P.O. Box 500, MS 223                                    *
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*    U.S.A.                                                  *
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