# Graph¶

A Simple Graph Example

Author: Wim Lavrijsen
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Tuesday, June 22, 2021 at 08:30 AM.

In [ ]:
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

In [ ]:
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.

Draw all canvases

In [ ]:
from ROOT import gROOT
gROOT.GetListOfCanvases().Draw()