gr002_errors.py File Reference

Detailed Description

Create and draw a graph with error bars.

If more graphs are needed, see the gr03_err2gr.C tutorial

See the TGraphErrors documentation

 
import numpy as np
import ROOT
 
c1 = ROOT.TCanvas("c1", "A Simple Graph with error bars", 200, 10, 700, 500)
 
c1.SetGrid()
c1.GetFrame().SetBorderSize(12)
 
#  We will use the constructor requiring: the number of points, arrays containing the x-and y-axis values, and arrays with the x- andy-axis errors
 
n = 10
x = np.array([-0.22, 0.05, 0.25, 0.35, 0.5, 0.61, 0.7, 0.85, 0.89, 0.95])
y = np.array([1, 2.9, 5.6, 7.4, 9, 9.6, 8.7, 6.3, 4.5, 1])
ex = np.array([0.05, 0.1, 0.07, 0.07, 0.04, 0.05, 0.06, 0.07, 0.08, 0.05])
ey = np.array([0.8, 0.7, 0.6, 0.5, 0.4, 0.4, 0.5, 0.6, 0.7, 0.8])
 
# If all x-axis errors should zero, just provide a single 0 in place of ex
gr = ROOT.TGraphErrors(n, x, y, ex, ey)
 
gr.SetTitle("TGraphErrors Example")
gr.SetMarkerColor(4)
gr.SetMarkerStyle(21)
 
# To draw in a new/empty canvas or pad, include the option "A" so that the axes are drawn (leave it out if the graph is to be drawn on top of an existing plot
gr.Draw("ALP")
 
c1.Update()

Author

Rene Brun, Jamie Gooding

Definition in file gr002_errors.py.