# Constrain in TFraction Fitter Class

Hello,

We are trying to fit two MC histograms with data using TFraction Fitter Class.
In that macro there is a line:
fit->Constrain(parameter # ,lower ,higher)

Can anybody explain what is this parameter number and how one can set the lower and higher limit?

regards

Hi,

Thjis method set th elower and upper limit on the parameter (by default they are -inf, +inf). The parameter number is the one following the order given in the input array of TH1* given in the constructor.

See the reference doc at root.cern.ch/root/htmldoc/TFract … :Constrain

Best Regards

Lorenzo