gr005_apply.py File Reference

Detailed Description

A macro to demonstrate the functionality of TGraph::Apply() method.

TGraph::Apply applies a function f to all the data TGraph points, f may be a 1-D function TF1 or 2-d function TF2. The Y values of the graph are replaced by the ROOT.values computed using the function.

The Apply() method can be used as well for TGraphErrors and TGraphAsymmErrors.

 
import numpy as np
import ROOT
 
npoints = 3
xaxis = np.array([1.0, 2.0, 3.0])
yaxis = np.array([10.0, 20.0, 30.0])
 
gr1 = ROOT.TGraph(npoints, xaxis, yaxis)
ff = ROOT.TF2("ff", "-1./y")  # Defining the function `f`
 
c1 = ROOT.TCanvas("c1", "c1", 0, 0, 700, 500)
c1.Divide(2, 1)
 
c1.cd(1)
gr1.DrawClone("A*")  # Using DrawClone to create a copy of the graph in the canvas.
c1.cd(2)
gr1.Apply(ff)  # Applies the function `f` to all the data TGraph points
gr1.Draw("A*")
# Without DrawClone, the modifications to gr1 via Apply(ff) are reflected in the original graph
# displayed in c1 (the two drawn graphs are not independent).

Author

Miro Helbich, Jamie Gooding

Definition in file gr005_apply.py.