[ROOT] error calc. in TProfile

From: Aihong Tang (aihong@cnr.physics.kent.edu)
Date: Tue Jul 16 2002 - 21:50:17 MEST


Hi,

Could anybody tell me why errors are identical in all
bins in TProfile when that profile is filled with small values?

The problem happens in ROOT 3.02.07, If I repeat the same thing
in ROOT 3.02.00, everything looks fine.
 
The code is :

==================test.C=====================
#include "TProfile.h"
#include "float.h"
#include "TRandom.h"
#include "TString.h"
#include "TCanvas.h"
#include "iostream.h"

void test(){
  TRandom rd;

  TProfile*  hprof= new TProfile("test", "test", 100,-4., 4., -1.*FLT_MAX, 
FLT_MAX, "");

 Float_t px, py, pz;
  for ( Int_t j=0; j<25; j++) {
     rd.Rannor(px,py);
     pz = px*px + py*py;
     hprof->Fill(px,pz*1e-7); <======== errors are calc. correctly if 
*1e-7 is removed from this line. It can be also calc. correctly if run in ROOT 3.02.00
  }
   
  hprof->Print("all");
  TCanvas *c1 = new TCanvas("c1","Profile histogram example",200,10,700,500);
  hprof->Draw();
}
========================================

Errors are shown the same for all bins in the following output:

----------------------------------------

  *******************************************
  *                                         *
  *        W E L C O M E  to  R O O T       *
  *                                         *
  *   Version   3.02/07      1 March 2002   *
  *                                         *
  *  You are welcome to visit our Web site  *
  *          http://root.cern.ch            *
  *                                         *
  *******************************************

Compiled for linux with thread support.

CINT/ROOT C/C++ Interpreter version 5.15.25, Jan 6 2002
Type ? for help. Commands must be C++ statements.
Enclose multiple statements between { }.

Welcome to the ROOT tutorials


Type ".x demos.C" to get a toolbar from which to execute the demos

Type ".x demoshelp.C" to see the help window

 *** Start at Date : Tue Jul 16 15:36:50 2002
QAInfo:You are using STAR_LEVEL : pro, ROOT_LEVEL : 3.02.07 and node : 
rcas6015.rcf.bnl.gov 
root4star [0] .x test.C++
Info in <ACLiC>: creating shared library 
/direct/star+data10/GC/aihong/anaSimV1_short/V2_5Pct_V1Vary_New/job4/dir8Test/./test_C.so
In file included from 
/direct/star+data10/GC/aihong/anaSimV1_short/V2_5Pct_V1Vary_New/job4/dir8Test/filexIyM7Z.h:29,
                 from 
/direct/star+data10/GC/aihong/anaSimV1_short/V2_5Pct_V1Vary_New/job4/dir8Test/./filexIyM7Z.C:5:
/direct/star+data10/GC/aihong/anaSimV1_short/V2_5Pct_V1Vary_New/job4/dir8Test/./test.C: 
In function 
`void test ()':
/direct/star+data10/GC/aihong/anaSimV1_short/V2_5Pct_V1Vary_New/job4/dir8Test/./test.C:25: 
warning: unused
variable `TCanvas *c1'
TH1.Print Name= test, Entries= 25, Total sum= 2.96441e-06
 fSumw[0]=0, x=-4.04, error=0
//bla... bla...
 fSumw[32]=2.96728e-07, x=-1.48, error=5.04825e-08
 fSumw[33]=0, x=-1.4, error=0
 fSumw[34]=0, x=-1.32, error=0
 fSumw[35]=1.60949e-07, x=-1.24, error=5.04825e-08
 fSumw[36]=0, x=-1.16, error=0
 fSumw[37]=3.59341e-07, x=-1.08, error=5.04825e-08
 fSumw[38]=0, x=-1, error=0
 fSumw[39]=0, x=-0.92, error=0
 fSumw[40]=0, x=-0.84, error=0
 fSumw[41]=0, x=-0.76, error=0
 fSumw[42]=5.56881e-08, x=-0.68, error=5.04825e-08
 fSumw[43]=1.46839e-07, x=-0.6, error=5.04825e-08
 fSumw[44]=2.11833e-07, x=-0.52, error=5.04825e-08
 fSumw[45]=2.29327e-07, x=-0.44, error=5.04825e-08
 fSumw[46]=2.87134e-07, x=-0.36, error=5.04825e-08
 fSumw[47]=3.0389e-07, x=-0.28, error=5.04825e-08
 fSumw[48]=0, x=-0.2, error=0
 fSumw[49]=0, x=-0.12, error=0
 fSumw[50]=0, x=-0.04, error=0
 fSumw[51]=0, x=0.04, error=0
 fSumw[52]=1.50715e-07, x=0.12, error=5.04825e-08
 fSumw[53]=8.96748e-08, x=0.2, error=5.04825e-08
 fSumw[54]=0, x=0.28, error=0
 fSumw[55]=9.49502e-08, x=0.36, error=5.04825e-08
 fSumw[56]=0, x=0.44, error=0
 fSumw[57]=3.50281e-08, x=0.52, error=5.04825e-08
 fSumw[58]=0, x=0.6, error=0
 fSumw[59]=0, x=0.68, error=0
 fSumw[60]=0, x=0.76, error=0
 fSumw[61]=0, x=0.84, error=0
 fSumw[62]=1.21321e-07, x=0.92, error=5.04825e-08
 fSumw[63]=1.92461e-07, x=1, error=5.04825e-08
 fSumw[64]=0, x=1.08, error=0
 fSumw[65]=0, x=1.16, error=0
 fSumw[66]=2.2853e-07, x=1.24, error=5.04825e-08

----------------------------------------------------


Thanks!

Aihong



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