graph.py

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## \file
## \ingroup tutorial_pyroot
## \notebook
## A Simple Graph Example
##
## \macro_image
## \macro_output
## \macro_code
##
## \author Wim Lavrijsen
 
from __future__ import print_function
from ROOT import TCanvas, TGraph
from ROOT import gROOT
from math import sin
from array import array
 
 
c1 = TCanvas( 'c1', 'A Simple Graph Example', 200, 10, 700, 500 )
 
c1.SetFillColor( 42 )
c1.SetGrid()
 
n = 20
x, y = array( 'd' ), array( 'd' )
 
for i in range( n ):
   x.append( 0.1*i )
   y.append( 10*sin( x[i]+0.2 ) )
   print(' i %i %f %f ' % (i,x[i],y[i]))
 
gr = TGraph( n, x, y )
gr.SetLineColor( 2 )
gr.SetLineWidth( 4 )
gr.SetMarkerColor( 4 )
gr.SetMarkerStyle( 21 )
gr.SetTitle( 'a simple graph' )
gr.GetXaxis().SetTitle( 'X title' )
gr.GetYaxis().SetTitle( 'Y title' )
gr.Draw( 'ACP' )
 
# TCanvas.Update() draws the frame, after which one can change it
c1.Update()
c1.GetFrame().SetFillColor( 21 )
c1.GetFrame().SetBorderSize( 12 )
c1.Modified()
c1.Update()
# If the graph does not appear, try using the "i" flag, e.g. "python3 -i graph.py"
# This will access the interactive mode after executing the script, and thereby persist
# long enough for the graph to appear.