rf502_wspacewrite.py

# /
#
# 'ORGANIZATION AND SIMULTANEOUS FITS' ROOT.RooFit tutorial macro #502
#
# Creating and writing a workspace
#
#
# 07/2008 - Wouter Verkerke
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# /


import ROOT


def rf502_wspacewrite():
    # C r e a t e   m o d e l   a n d   d a t a s e t
    # -----------------------------------------------

    # Declare observable x
    x = ROOT.RooRealVar("x", "x", 0, 10)

    # Create two Gaussian PDFs g1(x,mean1,sigma) anf g2(x,mean2,sigma) and
    # their parameters
    mean = ROOT.RooRealVar("mean", "mean of gaussians", 5, 0, 10)
    sigma1 = ROOT.RooRealVar("sigma1", "width of gaussians", 0.5)
    sigma2 = ROOT.RooRealVar("sigma2", "width of gaussians", 1)

    sig1 = ROOT.RooGaussian("sig1", "Signal component 1", x, mean, sigma1)
    sig2 = ROOT.RooGaussian("sig2", "Signal component 2", x, mean, sigma2)

    # Build Chebychev polynomial p.d.f.
    a0 = ROOT.RooRealVar("a0", "a0", 0.5, 0., 1.)
    a1 = ROOT.RooRealVar("a1", "a1", -0.2, 0., 1.)
    bkg = ROOT.RooChebychev("bkg", "Background", x, ROOT.RooArgList(a0, a1))

    # Sum the signal components into a composite signal p.d.f.
    sig1frac = ROOT.RooRealVar(
        "sig1frac", "fraction of component 1 in signal", 0.8, 0., 1.)
    sig = ROOT.RooAddPdf(
        "sig", "Signal", ROOT.RooArgList(sig1, sig2), ROOT.RooArgList(sig1frac))

    # Sum the composite signal and background
    bkgfrac = ROOT.RooRealVar("bkgfrac", "fraction of background", 0.5, 0., 1.)
    model = ROOT.RooAddPdf(
        "model", "g1+g2+a", ROOT.RooArgList(bkg, sig), ROOT.RooArgList(bkgfrac))

    # Generate a data sample of 1000 events in x from model
    data = model.generate(ROOT.RooArgSet(x), 1000)

    # C r e a t e   w o r k s p a c e , m p o r t   d a t a   a n d   m o d e l
    # -----------------------------------------------------------------------------

    # Create a empty workspace
    w = ROOT.RooWorkspace("w", "workspace")

    # Import model and all its components into the workspace
    getattr(w, 'import')(model)

    # Import data into the workspace
    getattr(w, 'import')(data)

    # Print workspace contents
    w.Print()

    # S a v e   w o r k s p a c e   i n   f i l e
    # -------------------------------------------

    # Save the workspace into a ROOT file
    w.writeToFile("rf502_workspace.root")

    # Workspace will remain in memory after macro finishes
    ROOT.gDirectory.Add(w)


if __name__ == "__main__":
    rf502_wspacewrite()