#define Ndim 4
#define NN 5

//this is a test for y = 0.1*x[0] + 0.2*x[1] + 0.3*x[2] + 0.4*x[3]
void test()
{

// Double_t *x=new Double_t[NN*Ndim];
// Double_t *y=new Double_t[NN];
 double x[NN*Ndim];
 double y[5] = {1.1, 2.1, 2.9, 4.05, 5.1};
 double e[5] = {0.1};

 for(int i=0; i<NN; i++)
  for(int j=0; j<Ndim; j++)
   x[j+i*j]  = i+1;

 TLinearFitter *lf=new TLinearFitter(Ndim);
// lf->SetFormula("[0]*x[0]++[1]*x[1]++[2]*x[2]++[3]*x[3]");
 lf->SetFormula("x[0]++x[1]++x[2]++x[3]");

 lf->AssignData(NN, Ndim, x, y, e);
// lf->FixParameter(1, 0.1);
 lf->Eval();
 TVectorD params;
 TVectorD errors;
 lf->GetParameters(params);
 lf->GetErrors(errors);
 for (Int_t i=0; i<Ndim; i++)
      printf("par[%d]=%f+-%f\n", i, params(i), errors(i));
   Double_t chisquare=lf->GetChisquare();
   printf("chisquare=%f\n", chisquare);

}