doc/v622/tStudent_8py.html

from ROOT import TH1D, TF1, TCanvas, kRed, kBlue

import ROOT


# This is the way to force load of MathMore in Cling

ROOT.Math.MathMoreLibrary.Load()


# Create the pdf and the cumulative distributions

n = 100

a = -5.

b = 5.

pdf = TF1("pdf", "ROOT::Math::tdistribution_pdf(x,3.0)", a, b)

cum = TF1("cum", "ROOT::Math::tdistribution_cdf(x,3.0)", a, b)


# Create the histogram and fill it with the quantiles

quant = TH1D("quant", "", 9, 0, 0.9)


for i in range(1, 10):

    quant.Fill((i-0.5)/10.0, ROOT.Math.tdistribution_quantile(0.1 * i,

                                                              3.0))


# For each quantile fill with the pdf

xx = []

xx.append(-1.5)

for i in range(1, 9):

    xx.append(quant.GetBinContent(i))

xx.append(1.5)


pdfq = []

for i in range(9):

    nbin = int(n * (xx[i+1] - xx[i]) / 3.0 + 1.0)

    name = "pdf%d" % i

    pdfq.append(TH1D(name, "", nbin, xx[i], xx[i+1]))

    for j in range(1, nbin):

        x = j * (xx[i+1] - xx[i]) / nbin + xx[i]

        pdfq[i].SetBinContent(j, ROOT.Math.tdistribution_pdf(x, 3))


# Create the Canvas and divide in four draws, for every draw set the line width

# the title, and the line color.

Canvas = TCanvas("DistCanvas", "Student Distribution graphs", 10, 10, 800, 700)

pdf.SetTitle("Student t distribution function")

cum.SetTitle("Cumulative for Student t")

quant.SetTitle("10-quantiles  for Student t")

Canvas.Divide(2, 2)

Canvas.cd(1)

pdf.SetLineWidth(2)

pdf.DrawCopy()

Canvas.cd(2)

cum.SetLineWidth(2)

cum.SetLineColor(kRed)

cum.Draw()

Canvas.cd(3)

quant.Draw()

quant.SetLineWidth(2)

quant.SetLineColor(kBlue)

quant.SetStats(0)

Canvas.cd(4)

pdfq[0].SetTitle("Student t & its quantiles")

pdf.SetTitle("")

pdf.Draw()

pdfq[0].SetTitle("Student t & its quantiles")


# Set the colors in every quantile.

i = 1

for pd in pdfq[1:]:

    pd.SetStats(0)

    i += 1

    pd.SetFillColor(i)

    pd.Draw("same")

Canvas.Modified()

TCanvas
The Canvas class.
Definition: TCanvas.h:27

TF1
1-Dim function class
Definition: TF1.h:210

TH1D
1-D histogram with a double per channel (see TH1 documentation)}
Definition: TH1.h:614

int

ROOT::Math::tdistribution_pdf
double tdistribution_pdf(double x, double r, double x0=0)
Probability density function of Student's t-distribution.
Definition: PdfFuncMathCore.h:555

ROOT::Math::tdistribution_quantile
double tdistribution_quantile(double z, double r)
Inverse ( ) of the cumulative distribution function of the lower tail of Student's t-distribution (td...
Definition: QuantFuncMathMore.cxx:20