Hi Kevin. To use combinations of predefined functions, you have to first create a function that is that combo, and then fit using that function: TF1* f1 = new TF1("f1", "gaus(0)+expo(3)"); f1->SetParameters(1, 2, 3, 4, 5); // or some reasonable start values h1->Fit("f1"); // NB: h1->Fit("gaus(0)+expo(3)") won't work To the ROOT developers: I know this seems to be a trivial amount of typing to achieve combo fits, but easy and quick fitting using different combinations of functions is something I miss from the old PAW / MinFit days. If syntax like h1->Fit("gaus(0)+expo(3)+(3*x-1)"); could be added, it would be a nice feature to have. Perhaps if the string isn't recognized as a function name, you could attempt to parse it and create a temporary function (similar to how TTree::Draw() creates a temporary histogram) and fit using that function. Happy fitting, Stephen On Tue, 27 Jun 2000, Kevin M. Rhodes wrote: > I'm trying to fit an histogram with a simple addition of two root-defined > functions, by doing gaus+expo. Is there something special that I need to > do to get this to work? > > > Kevin Rhodes > UW Madison > Amanda Project >
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