From: Arthur E. Snyder <snyder_at_slac.stanford.edu>

Date: Tue, 18 Oct 2005 11:35:32 -0700 (PDT)

Double_t pars[100];

f->GetParameters(pars);

Double_t dPar=fabs(pars[par])*eps;

if(dPar<eps) dPar=eps;

pars[par]+=dPar;

Double_t iUp=f->Integral(lo,up,pars)/Common::binSize; pars[par]-=2.0*dPar;

Double_t iLo=f->Integral(lo,up,pars)/Common::binSize; return (iUp-iLo)/2.0/dPar;

}

Date: Tue, 18 Oct 2005 11:35:32 -0700 (PDT)

I don't think there is (though such things are some times hard to find). I
just compute the derivatives numerical myself, so:

Double_t dIntegral(TF1* f,Double_t lo,Double_t up,Int_t par,Double_t eps)
{

Int_t nPar=f->GetNpar();

if(par<0) return 0.0; if(par>=nPar) return 0.0; if(nPar>=100) return 0.0;

Double_t pars[100];

f->GetParameters(pars);

Double_t dPar=fabs(pars[par])*eps;

if(dPar<eps) dPar=eps;

pars[par]+=dPar;

Double_t iUp=f->Integral(lo,up,pars)/Common::binSize; pars[par]-=2.0*dPar;

Double_t iLo=f->Integral(lo,up,pars)/Common::binSize; return (iUp-iLo)/2.0/dPar;

}

It would be nice if ROOT provide such functions and error calculations as well as thing like moment integrals, etc. Maybe it does and I just can't find them (in which case somebody will tell us ...).

-Art S.

A.E. Snyder, Group EC \!c*p?/ SLAC Mail Stop #95 ((. .)) Box 4349 | Stanford, Ca, USA, 94309 '\|/` e-mail:snyder_at_slac.stanford.edu o phone:650-926-2701 _ http://www.slac.stanford.edu/~snyder BaBar FAX:650-926-2657 Collaboration

On Tue, 18 Oct 2005, Alberto Pulvirenti wrote:

*> Dear all,*

*>*

*> a question about functions.*

*> If I have a TF1 object coming from a best-fit operation, where*

*> parameters and their errors are set, I know that it is possible to*

*> calculate its integral between two values A and B.*

*> Is there a way to calculate also the error of this integral, taking into*

*> account the errors on the fitted parameters?*

*>*

*> Thanks, regards*

*>*

*> Alberto*

*>*

*>*

Received on Tue Oct 18 2005 - 20:38:01 MEST

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