flower-butterfly / histimator

A solution for performing maximum likelihood estimation on models built from histogram templates.

Histimator

A solution for performing maximum likelihood estimation on models built from histogram templates.

• Free software: GNU General Public License v3
• Documentation: https://histimator.readthedocs.io.

Usage

the histimator core directory has a file called Models containing the core HistiModel class.

the model is initialised:

from histimator.models import HistiModel
model = HistiModel("model name")

Each channel is defined as:

from histimodel.Channel import HistiChannel
SR = HistiChannel("SignalRegion")

data can be added to the channels as:

SR.SetData([list of data points])

any number of samples are defined as:

from histimator.models import HistiSample
sig = HistiSample("Signal")
bkg = HistiSample("Background")

each of which needs a histogram:

sig.SetHisto(numpy.histogram)
bkg.SetHisto(numpy.histogram)

currently the only parameters available are an overal normalisation on these templates. this is given with a name an initial value (default 1) and a range (default [0.1,10]). Currently no implementation is actually in place to tell Minuit about this range...:

sig.AddNorm("some_norm",1,0,3)

Finally, the samples must be added to the channel and this added to the model.:

SR.AddSample(sig)
SR.AddSample(bkg)
model.AddChannel(SR)

This model can now be evaluated using probfit Binned Likelihood function:

from iminuit import Minuit
from probfit import BinnedLH
blh = BinnedLH(model.pdf, data, bins=10, bound=bound, extended=True)
m = Minuit(blh, some_norm=0.5, error_some_norm=1.5)
m.migrad()

this has various built in plotting functionality.

Credits