Double_t func1D(Double_t *x, Double_t *par){
//1-D function
Double_t xx=x[0];
Double_t val=TMath::Abs(par[0]*sin(par[1]*xx)/xx);
return val;
}

Double_t func2D(Double_t *x, Double_t *par){
//symmetric gaussian in 2-D
Double_t xx=x[0];
Double_t yy=x[1];
Double_t val=par[0]*TMath::Exp(-((xx-par[1])*(xx-par[1])+(yy-par[1])*(yy-par[1])) /(2.*par[2]*par[2]));
return val;
}