I was wondering what the option “M” on TFit helped improve fits of data. And I was also curious if TFit used a least squares method with vertical or perpendicular offsets?

If I wanted to change the fitting methods, is it possible to retrieve to code for the TFit class, or do I need to write my own class and link it with the ROOT library?

Thanks so much for any help anyone can give,


There is no TFit class in the ROOT system.
There is a TVirtualFitter and TFitter class.
These classes are typically used by higher
level functions such as TH1::Fit or TGraph::Fit.
See comments in these two functions.
See also fitting examples in the tutorials, eg FittingDemo.C