[ROOT] Fitter

From: Ray Fliller III (rfliller@bnl.gov)
Date: Wed Oct 25 2000 - 22:53:06 MEST 

  Hello Rooters,

   I am using ROOT version 2.23/12 on Linux

   Is there a reason why when I call TGraph::Fit, in a loop, to fit 
different TGraphs with different functions I get a segmentation fault in 
my code??

Example

FitAll(Data *d)
{
  int i;
  TString title;
  char n[2];
  float chisq,diff,ddiff;

  for(i=0;i<4;i++){
    title="collin4";
    sprintf(&n,"%i",i);
    title+=n;
    d->canvas->cd(i+1);
    d->func[i]->SetRange(11,300);
    d->graph[i]->Fit(title,"RB");
  }
}

  in my class data this is an array of 4 TGraphErrorss and 4 TF1s (named 
collin40,collin41,collin42,collin43)  If I do this by hand, all is 
happy.  Put it in a macro I get:

root [8] FitAll(move4)                            
 **********
 **    1 **SET ERR           1
 **********
 **********
 **    5 **MIGRAD        5000        0.01
 **********
 MIGRAD MINIMIZATION HAS CONVERGED.
 MIGRAD WILL VERIFY CONVERGENCE AND ERROR MATRIX.
 FCN=1135.12 FROM MIGRAD    STATUS=CONVERGED     346 CALLS         347 
TOTAL
                     EDM=2.94214e-08    STRATEGY= 1      ERROR MATRIX 
ACCURATE 
  EXT PARAMETER                                   STEP         FIRST   
  NO.   NAME      VALUE            ERROR          SIZE      DERIVATIVE 
   1  Amplitude    1.00000e-00   1.80924e-10   5.00000e-01   4.54747e-12
   2  Movement(m)   7.37671e+00   3.42481e+00   1.28569e-03  -1.61017e-03
   3  Diffusion Rate(mm-mrad/s)^2   9.03821e-06   8.37974e-06   
3.15019e-09   6.57012e+02
   4  Zero time(s)   1.10661e+01   3.48938e-03   3.45107e-05  -3.02434e-02
   5  Constant     1.95906e+03   4.29638e+00   4.44481e-02  -4.41191e-05
 FCN=1135.12 FROM MIGRAD    STATUS=CONVERGED     346 CALLS         347 
TOTAL
                     EDM=2.94214e-08    STRATEGY= 1      ERROR MATRIX 
ACCURATE 
  EXT PARAMETER                                   STEP         FIRST   
  NO.   NAME      VALUE            ERROR          SIZE      DERIVATIVE 
   1  Amplitude    1.00000e-00   1.80924e-10   5.00000e-01   4.54747e-12
   2  Movement(m)   7.37671e+00   3.42481e+00   1.28569e-03  -1.61017e-03
   3  Diffusion Rate(mm-mrad/s)^2   9.03821e-06   8.37974e-06   
3.15019e-09   6.57012e+02
   4  Zero time(s)   1.10661e+01   3.48938e-03   3.45107e-05  -3.02434e-02
   5  Constant     1.95906e+03   4.29638e+00   4.44481e-02  -4.41191e-05
 
 *** Break *** segmentation violation
Root > Function FitAll() busy flag cleared

It crashes at the i=1 call data->graph[i]->Fit(title,"RB")

All ranges, bounardaries, etc., are properly initialized.  Like I said, 
if I do this by hand (ie, I am the for statement), all is good, if ROOT 
is the for statment, all is anti-good.

Thanks for your help


==============================================================================
Ray Fliller: rfliller@bnl.gov      Office Phone: (631)-344-6124 
C-A Accelerator Physics     
Building 911
Brookhaven National Lab
Upton, NY 11973                    Office: Room 211
==============================================================================

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