How to use pyROOT 応用編 その3

任意関数での ヒストグラムの fitting

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1. #/bin/usr/env python  
2.   
3. import sys, math  
4. import ROOT  
5.   
6.   
7. class Linear:  
8.     def __call__(self, x, par):  
9.         return par[0] + x[0] * par[1]  
10.   
11. if __name__=='__main__':  
12.   
13.     cv  = ROOT.TCanvas("cv", "Fitting Example", 200, 10, 700, 500)  
14.   
15.     # create a linear function for fitting  
16.     f = ROOT.TF1('f', Linear(), -1., 1., 2)  
17.   
18.     # create histogram ( identify, Title, ?, xmin, xmax )  
19.     h = ROOT.TH1F('h', 'px', 100, -1., 1.)  
20.     f2= ROOT.TF1('f2', '6. + x * 4.5', -1, 1.)  
21.   
22.     h.FillRandom('f2', 10000)  
23.       
24.   
25.     # fits the hitstogram with the 'Linear' function  
26.     h.Fit(f)  
27.   
28.     # export  
29.     cv.Print("graphtest4.png")  
30.   
31.     # print results  
32.     par = f.GetParameters()  
33.     print 'fitting result: const = ', par[0], ', pitch = ', par[1]  

#/bin/usr/env python

import sys, math
import ROOT


class Linear:
    def __call__(self, x, par):
        return par[0] + x[0] * par[1]

if __name__=='__main__':

    cv  = ROOT.TCanvas("cv", "Fitting Example", 200, 10, 700, 500)

    # create a linear function for fitting
    f = ROOT.TF1('f', Linear(), -1., 1., 2)

    # create histogram ( identify, Title, ?, xmin, xmax )
    h = ROOT.TH1F('h', 'px', 100, -1., 1.)
    f2= ROOT.TF1('f2', '6. + x * 4.5', -1, 1.)

    h.FillRandom('f2', 10000)
    

    # fits the hitstogram with the 'Linear' function
    h.Fit(f)

    # export
    cv.Print("graphtest4.png")

    # print results
    par = f.GetParameters()
    print 'fitting result: const = ', par[0], ', pitch = ', par[1]

実行結果

$ python graphtest4.py
 FCN=101.388 FROM MIGRAD    STATUS=CONVERGED      29 CALLS          30 TOTAL
 EDM=2.65063e-16    STRATEGY= 1      ERROR MATRIX ACCURATE
  EXT PARAMETER                                   STEP         FIRST
  NO.   NAME      VALUE            ERROR          SIZE      DERIVATIVE
   1  p0           9.89861e+01   9.94918e-01   4.29016e-03  -2.65160e-08
   2  p1           7.57130e+01   1.55891e+00   6.72214e-03   8.21832e-09
Info in : file graphtest4.png has been created
fitting result: const =  98.9861239576 , pitch =  75.7130326833