example-landaugausfit

An example ROOT script that fits a Landau+Gaussian function to a ROOT histogram.

This package provides a pyroot implementation of the ROOT example: $ROOTSYS/tutorials/fit/langaus.C

The fitter is implemented by the class LanGausFit in the file langaus.py. The most basic usage is:

import ROOT
from langaus import LanGausFit
# create a histogram
histogram = ROOT.TH1D("hist", "hist", 100, 0.0, 10.)
histogram.FillRandom("gaus", 1000)
# fit the histogram
fit = LanGausFit()
func = fit.fit(histogram)
# The fitter return a ROOT TF1 (a 1D function).
func.Print()

The actual fit function is implemented inside langaus.C. If you want to copy this code into another package then you should remember to copy both files.

You can test the fitter by running the script from the command line.

python langaus.py -o testplot.eps

It will generate a Landau+Gaussian distribution, fit the distribution and save the plot to the provided file name. For more information see the help message:

python langaus.py -h

    usage: Test script for LanGaus fit. [-h] [--mpv MPV] [--sigma SIGMA]
                                    [--width WIDTH] [--nevents NEVENTS]
                                    [--xlow XLOW] [--xhigh XHIGH] [-o OUTPUT]

optional arguments:
  -h, --help            show this help message and exit
  --mpv MPV             Generate data with this Landau MPV
  --sigma SIGMA         Generate data with this Gaussian sigma
  --width WIDTH         Generate data with this Landau width.
  --nevents NEVENTS     Generate this many events.
  --xlow XLOW           Plot min x value
  --xhigh XHIGH         Plot max x value
  -o OUTPUT, --output OUTPUT
                        Output plot file name.