User defined fit function

ROOT
1

Hi,
How would someone go about defining a user function such as “gaus+gaus+pol2” then being able to use the “user” button on the FitPanel to fit a histogram using the slider bar (i.e is there a way to fit a user defined function between given points using the GUI interface rather than setting the parameters in the code each time?)

Thanks,
Nick

2

There are several methods, if you not need to take care of the normalization you can define the function as:

 TF1 *user = new TF1("user","gaus(0)+gaus(3)+pol12(6)")

The most important part is to name the function “user”, so when in the fit panel you chose the user defined function this function is called.

Before run the fit I think you need to set the initial parameters to value different by 0.