doc/v612/gerrors_8py.html

from ROOT import TCanvas, TGraphErrors
from ROOT import gROOT
from array import array
c1 = TCanvas( 'c1', 'A Simple Graph with error bars', 200, 10, 700, 500 )
c1.SetGrid()
c1.GetFrame().SetFillColor( 21 )
c1.GetFrame().SetBorderSize( 12 )
n = 10;
x  = array( 'f', [ -0.22, 0.05, 0.25, 0.35,  0.5, 0.61,  0.7, 0.85, 0.89, 0.95 ] )
ex = array( 'f', [  0.05,  0.1, 0.07, 0.07, 0.04, 0.05, 0.06, 0.07, 0.08, 0.05 ] )
y  = array( 'f', [     1,  2.9,  5.6,  7.4,  9.0,  9.6,  8.7,  6.3,  4.5,    1 ] )
ey = array( 'f', [  0.8,  0.7,  0.6,  0.5,  0.4,  0.4,  0.5,  0.6,  0.7,  0.8  ] )
gr = TGraphErrors( n, x, y, ex, ey )
gr.SetTitle( 'TGraphErrors Example' )
gr.SetMarkerColor( 4 )
gr.SetMarkerStyle( 21 )
gr.Draw( 'ALP' )
c1.Update()