**Next message:**Rene Brun: "Re: [ROOT] TF1 is not aware of the TMath functions"**Previous message:**Stilianos Kesisoglou: "[ROOT] TF1 is not aware of the TMath functions"**In reply to:**Stilianos Kesisoglou: "[ROOT] combining functions"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]

See the documentation of classes TF1 and TFormula: http://root.cern.ch/root/htmldoc/TF1.html http://root.cern.ch/root/htmldoc/TFormula.html In particular in TF1 the following paragraph: TF1 objects can reference other TF1 objects (thanks John Odonnell) of type A or B defined above.This excludes CINT interpreted functions and compiled functions. However, there is a restriction. A function cannot reference a basic function if the basic function is a polynomial polN. You can find a list of expressions/codes accepted in the basic functions at: http://root.cern.ch/root/htmldoc/TFormula.html#TFormula:Analyze Rene Brun On Sat, 12 Jun 2004, Stilianos Kesisoglou wrote: > Hi, > > I've encountered a problem when I was trying to combine two TF1 > functions, > and I am not sure if this is my mistake or is not implemented on ROOT yet. > > If I define: > > TF1 *bf = new TF1("bf","[0]+[1]*exp([2]*x)"); > TF1 *sf = new TF1("sf","[0]*exp(-0.5*(x-[1])*(x-[1])/[2]/[2])"); > > and then: > > TF1 *tf = new TF1("tf","bf+sf"); > > I get what I expect (i.e a function wich is the sum of the other > ones). > But if the one of the two is a user made function it fails, for > example > I want to use an asymmetric Gaussian for the signal: > > Double_t SkewGauss(Double_t *x, Double_t *pars) > { > here follows the definition of the function > } > > then the following fails: > > TF1 *bf = new TF1("bf","[0]+[1]*exp([2]*x)"); > TF1 *sf = new TF1("sf",SkewGauss,4); > > and then: > > TF1 *tf = new TF1("tf","bf+sf"); > > Is there anyway to do the above? Is there a canned SkewGauss > function? > (that would solve the problem). > > Stelios. > > P.S Is there any list of the canned functions that ROOT knows? I was > looking some > examples when I saw that ROOT knows about the "xygaus" which I > didn't knew. > Is there anywhere a list of all known functions? > > >

**Next message:**Rene Brun: "Re: [ROOT] TF1 is not aware of the TMath functions"**Previous message:**Stilianos Kesisoglou: "[ROOT] TF1 is not aware of the TMath functions"**In reply to:**Stilianos Kesisoglou: "[ROOT] combining functions"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]

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