[TDF] Add a profiles tutorial in Python

tutorials/dataframe/tdf003_profiles.py

+## \file
+## \ingroup tutorial_tdataframe
+## \notebook -nodraw
+## This tutorial illustrates how to use TProfiles in combination with the
+## TDataFrame. See the documentation of TProfile and TProfile2D to better
+## understand the analogy of this code with the example one.
+##
+## \macro_code
+##
+## \date February 2017
+## \author Danilo Piparo
+
+import ROOT
+TDataFrame = ROOT.ROOT.Experimental.TDataFrame
+
+# A simple helper function to fill a test tree: this makes the example
+# stand-alone.
+def fill_tree(treeName, fileName):
+    d = TDataFrame(25000)
+    d.Define("px", "gRandom->Gaus()")\
+     .Define("py", "gRandom->Gaus()")\
+     .Define("pz", "sqrt(px * px + py * py)")\
+     .Snapshot(treeName, fileName)
+
+
+
+# We prepare an input tree to run on
+fileName = "tdf003_profiles.root"
+treeName = "myTree"
+fill_tree(treeName, fileName)
+
+# We read the tree from the file and create a TDataFrame.
+columns = ROOT.vector('string')()
+columns.push_back("px")
+columns.push_back("py")
+columns.push_back("pz")
+d = TDataFrame(treeName, fileName, columns)
+
+# Create the profiles
+hprof1d = d.Profile1D(("hprof1d", "Profile of pz versus px", 64, -4, 4))
+hprof2d = d.Profile2D(("hprof2d", "Profile of pz versus px and py", 40, -4, 4, 40, -4, 4, 0, 20))
+
+# And Draw
+c1 = ROOT.TCanvas("c1", "Profile histogram example", 200, 10, 700, 500)
+hprof1d.Draw()
+c2 = ROOT.TCanvas("c2", "Profile2D histogram example", 200, 10, 700, 500)
+c2.cd()
+hprof2d.Draw()
+