When i fitting the histogram using fix parameter. How can i get the fitted grah's integral error?

[Wile_E_Coyote]

Integral error with a TF1 functoin not from fitting

Instead of “gaus” try “gausn” (normalized gaussian), then the “Constant” parameter will be the “peak area” (and you immediately get its error, too), not the “peak height”: gROOT->GetFunction("gaus")->Print(); gROOT->GetFunction("gausn")->Print();