multiFit.py

#!/usr/bin/env python
# encoding: utf-8
"""
multiFit.py

Created by Sam Cook on 2011-02-24.
Copyright (c) 2011 __MyCompanyName__. All rights reserved.
"""

  # Fitting multiple functions to different ranges of a 1-D histogram
  #    To see the output of this macro, click begin_html <a href="gif/multifit.gif" >here</a> end_html
  #         Example showing how to fit in a sub-range of an histogram
  #     An histogram is created and filled with the bin contents and errors
  #     defined in the table below.
  #     3 gaussians are fitted in sub-ranges of this histogram.
  #     A new function (a sum of 3 gaussians) is fitted on another subrange
  #     Note that when fitting simple functions, such as gaussians, the initial
  #     values of parameters are automatically computed by ROOT.
  #     In the more complicated case of the sum of 3 gaussians, the initial values
  #     of parameters must be given. In this particular case, the initial values
  #     are taken from the result of the individual fits.
  #   Author: Rene Brun


from ROOT import *
from time import sleep

def main():
    np = 49;
    x  = [1.913521, 1.953769, 2.347435, 2.883654, 3.493567,
        4.047560, 4.337210, 4.364347, 4.563004, 5.054247,
        5.194183, 5.380521, 5.303213, 5.384578, 5.563983,
        5.728500, 5.685752, 5.080029, 4.251809, 3.372246,
        2.207432, 1.227541, 0.8597788,0.8220503,0.8046592,
        0.7684097,0.7469761,0.8019787,0.8362375,0.8744895,
        0.9143721,0.9462768,0.9285364,0.8954604,0.8410891,
        0.7853871,0.7100883,0.6938808,0.7363682,0.7032954,
        0.6029015,0.5600163,0.7477068,1.188785, 1.938228,
        2.602717, 3.472962, 4.465014, 5.177035]

    h = TH1F("h","Example of several fits in subranges",np,85,134)
    h.SetMaximum(7)

    for i in range(np):
        h.SetBinContent(i+1,x[i])
    h.Draw()

    par = []
    g1    = TF1("g1","gaus",85,95)
    g2    = TF1("g2","gaus",98,108)
    g3    = TF1("g3","gaus",110,121)
    total = TF1("total","gaus(0)+gaus(3)+gaus(6)",85,125)
    
    total.SetLineColor(2)
    
    h.Fit(g1,"R")
    h.Fit(g2,"R+")
    h.Fit(g3,"R+")
    par = []
    par.append(g1.GetParameters())
    par.append(g2.GetParameters())
    par.append(g3.GetParameters())
    # print par
    for i in range (3):
        for j in range (3):
            total.FixParameter(j, par[i][j])
    h.Fit(total,"R+")
    sleep(60)

    


if __name__ == '__main__':
    main()