fit1.py File Reference

Detailed Description

Fit example.

TFile**     py-fillrandom.root   
 TFile*     py-fillrandom.root   
  KEY: TFormula   form1;1  abs(sin(x)/x)
  KEY: TF1  sqroot;1 x*gaus(0) + [3]*form1
  KEY: TH1F h1f;1 Test random numbers
Formula based function:     sqroot 
               sqroot : x*gaus(0) + [3]*form1 Ndim= 1, Npar= 4, Number= 0 
 Formula expression: 
   x*[p0]*exp(-0.5*((x-[p1])/[p2])*((x-[p1])/[p2]))+[p3]*(abs(sin(x)/x)) 
****************************************
Minimizer is Minuit2 / Migrad
Chi2                      =      198.935
NDf                       =          190
Edm                       =  1.49283e-07
NCalls                    =          149
p0                        =      33.1658   +/-   0.545703    
p1                        =      4.00667   +/-   0.0165304   
p2                        =     0.984663   +/-   0.0128238   
p3                        =      63.4464   +/-   1.33233     
fit1      : Real Time =   0.39 seconds Cpu Time =   0.38 seconds

 
import ROOT
from os import path
from ROOT import TCanvas, TFile, TPaveText
from ROOT import gROOT, gBenchmark
 
c1 = TCanvas( 'c1', 'The Fit Canvas', 200, 10, 700, 500 )
c1.SetGridx()
c1.SetGridy()
c1.GetFrame().SetFillColor( 21 )
c1.GetFrame().SetBorderMode(-1 )
c1.GetFrame().SetBorderSize( 5 )
 
gBenchmark.Start( 'fit1' )
#
# We connect the ROOT file generated in a previous tutorial
#
File = "py-fillrandom.root"
if (ROOT.gSystem.AccessPathName(File)) :
    ROOT.Info("fit1.py", File+" does not exist")
    exit()
 
fill = TFile(File)
 
#
# The function "ls()" lists the directory contents of this file
#
fill.ls()
 
#
# Get object "sqroot" from the file.
#
 
sqroot = gROOT.FindObject( 'sqroot' )
sqroot.Print()
 
#
# Now fit histogram h1f with the function sqroot
#
h1f = gROOT.FindObject( 'h1f' )
h1f.SetFillColor( 45 )
h1f.Fit( 'sqroot' )
 
# We now annotate the picture by creating a PaveText object
# and displaying the list of commands in this macro
#
fitlabel = TPaveText( 0.6, 0.3, 0.9, 0.80, 'NDC' )
fitlabel.SetTextAlign( 12 )
fitlabel.SetFillColor( 42 )
fitlabel.ReadFile(path.join(str(gROOT.GetTutorialDir()), 'pyroot', 'fit1_py.py'))
fitlabel.Draw()
c1.Update()
gBenchmark.Show( 'fit1' )

Author

Wim Lavrijsen

Definition in file fit1.py.