new_contents: ## \file
  ## \ingroup tutorial_graphs
  ## \notebook -js
  ## This macro illustrates the use of the time axis on a TGraph
  ## with data read from a text file containing the SWAN usage
  ## statistics during July 2017.
  ##
  ## \macro_image
  ## \macro_code
  ##
  ## \authors Danilo Piparo, Olivier Couet
  
  import ROOT
  
  # Open the data file. This csv contains the usage statistics of a CERN IT
  # service, SWAN, during two weeks. We would like to plot this data with
  # ROOT to draw some conclusions from it.
  dirName = str(ROOT.gROOT.GetTutorialDir())
  dirName += "/graphs/"
  dirName= dirName.replace("/./", "/")
  inputFileName = "%s/SWAN2017.dat" %dirName
  
  # Create the time graph
  g = ROOT.TGraph()
  g.SetTitle("SWAN Users during July 2017;Time;Number of Users")
  
  # Read the data and fill the graph with time along the X axis and number
  # of users along the Y axis
  
  lines = open(inputFileName, "r").readlines()
  
  for i, line in enumerate(lines):
      d, h, value = line.split()
      g.SetPoint(i, ROOT.TDatime("%s %s" %(d,h)).Convert(), float(value))
  
  # Draw the graph
  c = ROOT.TCanvas("c", "c", 950, 500)
  c.SetLeftMargin(0.07)
  c.SetRightMargin(0.04)
  c.SetGrid()
  g.SetLineWidth(3)
  g.SetLineColor(ROOT.kBlue)
  g.Draw("al")
  g.GetYaxis().CenterTitle()
  
  # Make the X axis labelled with time
  xaxis = g.GetXaxis()
  xaxis.SetTimeDisplay(1)
  xaxis.CenterTitle()
  xaxis.SetTimeFormat("%a %d")
  xaxis.SetTimeOffset(0)
  xaxis.SetNdivisions(-219)
  xaxis.SetLimits(ROOT.TDatime(2017, 7, 3, 0, 0, 0).Convert(), ROOT.TDatime(2017, 7, 22, 0, 0, 0).Convert())
  xaxis.SetLabelSize(0.025)
  xaxis.CenterLabels()
  
  
subject: Add Python tutorial about time series