doc/v620/rf111__derivatives_8py.html

import ROOT


# Set up model

# ---------------------


# Declare variables x,mean, with associated name, title, value and allowed

# range

x = ROOT.RooRealVar("x", "x", -10, 10)

mean = ROOT.RooRealVar("mean", "mean of gaussian", 1, -10, 10)

sigma = ROOT.RooRealVar("sigma", "width of gaussian", 1, 0.1, 10)


# Build gaussian p.d.f in terms of x, and sigma

gauss = ROOT.RooGaussian("gauss", "gaussian PDF", x, mean, sigma)


# Create and plot derivatives w.r.t. x

# ----------------------------------------------------------------------


# Derivative of normalized gauss(x) w.r.t. observable x

dgdx = gauss.derivative(x, 1)


# Second and third derivative of normalized gauss(x) w.r.t. observable x

d2gdx2 = gauss.derivative(x, 2)

d3gdx3 = gauss.derivative(x, 3)


# Construct plot frame in 'x'

xframe = x.frame(ROOT.RooFit.Title("d(Gauss)/dx"))


# Plot gauss in frame (i.e. in x)

gauss.plotOn(xframe)


# Plot derivatives in same frame

dgdx.plotOn(xframe, ROOT.RooFit.LineColor(ROOT.kMagenta))

d2gdx2.plotOn(xframe, ROOT.RooFit.LineColor(ROOT.kRed))

d3gdx3.plotOn(xframe, ROOT.RooFit.LineColor(ROOT.kOrange))


# Create and plot derivatives w.r.t. sigma

# ------------------------------------------------------------------------------


# Derivative of normalized gauss(x) w.r.t. parameter sigma

dgds = gauss.derivative(sigma, 1)


# Second and third derivative of normalized gauss(x) w.r.t. parameter sigma

d2gds2 = gauss.derivative(sigma, 2)

d3gds3 = gauss.derivative(sigma, 3)


# Construct plot frame in 'sigma'

sframe = sigma.frame(ROOT.RooFit.Title(

    "d(Gauss)/d(sigma)"), ROOT.RooFit.Range(0., 2.))


# Plot gauss in frame (i.e. in x)

gauss.plotOn(sframe)


# Plot derivatives in same frame

dgds.plotOn(sframe, ROOT.RooFit.LineColor(ROOT.kMagenta))

d2gds2.plotOn(sframe, ROOT.RooFit.LineColor(ROOT.kRed))

d3gds3.plotOn(sframe, ROOT.RooFit.LineColor(ROOT.kOrange))


# Draw all frames on a canvas

c = ROOT.TCanvas("rf111_derivatives", "rf111_derivatives", 800, 400)

c.Divide(2)

c.cd(1)

ROOT.gPad.SetLeftMargin(0.15)

xframe.GetYaxis().SetTitleOffset(1.6)

xframe.Draw()

c.cd(2)

ROOT.gPad.SetLeftMargin(0.15)

sframe.GetYaxis().SetTitleOffset(1.6)

sframe.Draw()


c.SaveAs("rf111_derivatives.png")