[tutorials] Convert some TH1 tutorials to python

tutorials/hist/hist000_TH1_first.py

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+## \file
+## \ingroup tutorial_hist
+## Hello World example for TH1
+##
+## Shows how to create, fill and write a histogram to a ROOT file.
+##
+## \macro_code
+## \macro_output
+##
+## \date November 2024
+## \author Giacomo Parolini (CERN)
+
+import ROOT
+
+# Open the file to write the histogram to
+with ROOT.TFile.Open("outfile.root", "RECREATE") as outFile:
+   # Create the histogram object
+   # There are several constructors you can use (see TH1). In this example we use the
+   # simplest one, accepting a number of bins and a range.
+   histogram = ROOT.TH1D("histogram", "My first ROOT histogram", nbinsx = 30, xlow = 0.0, xup = 10.0)
+
+   # Fill the histogram. In this simple example we use a fake set of data.
+   # The 'D' in TH1D stands for 'double', so we fill the histogram with doubles.
+   # In general you should prefer TH1D over TH1F unless you have a very specific reason
+   # to do otherwise.
+   values = [1, 2, 3, 3, 3, 4, 3, 2, 1, 0]
+   for val in values:
+      histogram.Fill(val)
+
+   # Write the histogram to `outFile`.
+   outFile.WriteObject(histogram, histogram.GetName())
+
+   # When `with` block exits, `outFile` will close itself and write its contents to disk.

tutorials/hist/hist001_TH1_fillrandom.py

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+## \file
+## \ingroup tutorial_hist
+## \notebook
+## Fill a 1D histogram with random values using predefined functions
+##
+## \macro_image
+## \macro_code
+##
+## \date November 2024
+## \author Giacomo Parolini
+import ROOT
+
+# Create a one dimensional histogram and fill it with a gaussian distribution
+h1d = ROOT.TH1D("h1d", "Test random numbers", nbinsx = 200, xlow = 0.0, xup = 10.0)
+
+# "gaus" is a predefined ROOT function. Here we are filling the histogram with
+# 10000 values sampled from that distribution.
+h1d.FillRandom("gaus", 10000)
+
+# Open a ROOT file and save the histogram
+with ROOT.TFile.Open("fillrandom.root", "RECREATE") as myfile:
+   myfile.WriteObject(h1d, h1d.GetName())

tutorials/hist/hist002_TH1_fillrandom_userfunc.py

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+## \file
+## \ingroup tutorial_hist
+## \notebook
+## Fill a 1D histogram from a user-defined parametric function.
+##
+## \macro_image
+## \macro_code
+##
+## \date November 2024
+## \author Rene Brun, Giacomo Parolini
+import ROOT
+
+# Create a user-defined formula.
+# A function (any dimension) or a formula may reference an already defined formula
+form1 = ROOT.TFormula("form1", "abs(sin(x)/x)")
+
+# Create a 1D function using the formula defined above and the predefined "gaus" formula.
+rangeMin = 0.0
+rangeMax = 10.0
+sqroot = ROOT.TF1("sqroot", "x*gaus(0) + [3]*form1", rangeMin, rangeMax)
+sqroot.SetLineColor(4)
+sqroot.SetLineWidth(6)
+# Set parameters to the functions "gaus" and "form1".
+gausScale = 10.0  # [0]
+gausMean = 4.0    # [1]
+gausVar = 1.0     # [2]
+form1Scale = 20.0 # [3]
+sqroot.SetParameters(gausScale, gausMean, gausVar, form1Scale)
+
+# Create a one dimensional histogram and fill it following the distribution in function sqroot.
+h1d = ROOT.TH1D("h1d", "Test random numbers", 200, rangeMin, rangeMax)
+
+# Use our user-defined function to fill the histogram with random values sampled from it.
+h1d.FillRandom("sqroot", 10000)
+
+# Open a ROOT file and save the formula, function and histogram
+with ROOT.TFile.Open("fillrandom.root", "RECREATE") as myFile:
+   myFile.WriteObject(form1, form1.GetName())
+   myFile.WriteObject(sqroot, sqroot.GetName())
+   myFile.WriteObject(h1d, h1d.GetName())

tutorials/hist/hist003_TH1_draw.py

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+## \file
+## \ingroup tutorial_hist
+## \notebook
+## Draw a 1D histogram to a canvas.
+##
+## \note When using graphics inside a ROOT macro the objects must be created with `new`.
+##
+## \macro_image
+## \macro_code
+##
+## \date November 2024
+## \author Rene Brun, Giacomo Parolini
+import ROOT
+
+# Create and fill the histogram.
+# See hist002_TH1_fillrandom_userfunc.C for more information about this section.
+form1 = ROOT.TFormula("form1", "abs(sin(x)/x)")
+rangeMin = 0.0
+rangeMax = 10.0
+sqroot = ROOT.TF1("sqroot", "x*gaus(0) + [3]*form1", rangeMin, rangeMax)
+sqroot.SetLineColor(4)
+sqroot.SetLineWidth(6)
+sqroot.SetParameters(10.0, 4.0, 1.0, 20.0)
+
+nBins = 200
+h1d = ROOT.TH1D("h1d", "Test random numbers", nBins, rangeMin, rangeMax)
+
+h1d.FillRandom("sqroot", 10000)
+
+# Create a canvas and draw the histogram
+topX = 200
+topY = 10
+width = 700
+height = 900
+c1 = ROOT.TCanvas("c1", "The FillRandom example", topX, topY, width, height)
+
+# Split the canvas into two sections to plot both the function and the histogram
+# The TPad's constructor accepts the relative coordinates (0 to 1) of the pad's boundaries
+pad1 = ROOT.TPad("pad1", "The pad with the function", 0.05, 0.50, 0.95, 0.95)
+pad2 = ROOT.TPad("pad2", "The pad with the histogram", 0.05, 0.05, 0.95, 0.45)
+
+# Draw the two pads
+pad1.Draw()
+pad2.Draw()
+
+# Select pad1 to draw the next objects into
+pad1.cd()
+pad1.SetGridx()
+pad1.SetGridy()
+pad1.GetFrame().SetBorderMode(-1)
+pad1.GetFrame().SetBorderSize(5)
+
+# Draw the function in pad1
+sqroot.Draw()
+# Add a label to the function.
+# TPaveLabel's constructor accepts the pixel coordinates and the label string.
+lfunction = ROOT.TPaveLabel(5, 39, 9.8, 46, "The sqroot function")
+lfunction.Draw()
+c1.Update()
+
+# Select pad2 to draw the next objects into
+pad2.cd()
+pad2.GetFrame().SetBorderMode(-1)
+pad2.GetFrame().SetBorderSize(5)
+
+h1d.SetFillColor(45)
+h1d.Draw()
+c1.Update()