Fit problem

I want to draw an error function. The command I use is:
TF1 *f1 = new TF1('f1",“Double ROOT::Math::erf(Double x)”,0,1000);

ROOT returns : Bad numerical formula …
and that the function used has 0 parameters instead of 1.
How should I do it?
Thank you

TF1 *f1 = new TF1(“f1”, “TMath::Erf(x)”, 0, 1000);
TF1 *f1 = new TF1(“f1”, “ROOT::Math::erf(x)”, 0, 1000);

See class TF1 and class TFormula descriptions.