Piecewise fits

I would like to do a fit (preferably in RooFit) using a smooth piecewise function. I’m having trouble finding documentation on this. Sorry for the broadness of the question, but is there any built-in way to do this?

Numerical Minimization

Sorry, but I’m not entirely clear on the relevance of that page. Were you pointing out the “RosenBrock” function they build in the examples?

Sorry, you should be more precise on what you would like to do :

  • minimising a function ? (in this case the Rosenbrock example can be instructive)
  • fitting a data points with a function and use RooFit ?

You can look also at the ROOT primer and at the various course material which is linked from the ROOT Web page for this general questions


I’m trying to fit to an awkwardly shaped histogram. I would like to specify a few different shapes to be fit to different parts of the histogram and constrain these shapes to be smooth numerically at the boundaries between them.

I have not found any documentation that seems particularly relevant to this.


In this case the best is you create your own global function, that evaluates differently depending on the range and you put the smooth constraint in defining this function.
It is a problem a user needs to solve


Try this: