Hello, after I changed to ROOT v6 I got a weir error when running a fitting script. [image] The error looks like this Double_t TFormula____id14364857767516896690(Double_t *x,Double_t *p){ return p[2]*(1+2*TMath::Power(p[0])*0.8*TMath::Cos(TMath::DegToR... …

I tried “v6.08.06” and it indeed dies. But “v6.09.02” and “v6.10.00” are fine. So, try to upgrade your ROOT version to the newest one.