Double_t GetRand(TF1 *func, Double_t X_MIN, Double_t X_MAX, int seed )
{
Double_t Y_MAX;
Y_MAX = func->GetMaximum();
//std::cout << "Y_MAX=" << Y_MAX << std::endl;
TRandom2* r = new TRandom3(seed);
Double_t x =0;
Double_t y = r->Uniform();
Double_t f_y = 3e+6;
while(1)
{
x = r->Uniform(X_MIN, X_MAX);
//std::cout << "x=" << x << std::endl;
y = r->Uniform(0, Y_MAX);
//std::cout << "y=" << y << std::endl;
f_y = func->Eval(x);
//std::cout << "f_y=" << f_y << std::endl;
if(f_y > y)
break;
}
//std::cout << "x budur=" << x << std::endl;
return x;
}
void ThreeDFit() {
const int n = 1000;
double x[n], y[n], z[n], v[n];
double ev = 0.1;
// generate the data
TRandom2 r;
for (int i = 0; i < n; ++i) {
x[i] = r.Uniform(0,10);
y[i] = r.Uniform(0,10);
z[i] = r.Uniform(0,10);
v[i] = sin(x[i] ) + cos(y[i]) + z[i] + r.Gaus(0,ev);
}
// create a 3d binned data structure
ROOT::Fit::BinData data(n,3);
double xx[3];
for(int i = 0; i < n; ++i) {
xx[0] = x[i];
xx[1] = y[i];
xx[2] = z[i];
// add the 3d-data coordinate, the predictor value (v[i]) and its errors
data.Add(xx, v[i], ev);
}
TF3 * f3 = new TF3("f3","[0] * sin(x) + [1] * cos(y) + [2] * z",0,10,0,10,0,10);
f3->SetParameters(2,2,2);
ROOT::Fit::Fitter fitter;
// wrapped the TF1 in a IParamMultiFunction interface for teh Fitter class
ROOT::Math::WrappedMultiTF1 wf(*f3,3);
fitter.SetFunction(wf);
//
bool ret = fitter.Fit(data);
if (ret) {
const ROOT::Fit::FitResult & res = fitter.Result();
// print result (should be around 1)
res.Print(std::cout);
// copy all fit result info (values, chi2, etc..) in TF3
f3->SetFitResult(res);
// test fit p-value (chi2 probability)
double prob = res.Prob();
if (prob < 1.E-2)
Error("exampleFit3D","Bad data fit - fit p-value is %f",prob);
else
std::cout << "Good fit : p-value = " << prob << std::endl;
}
else
Error("exampleFit3D","3D fit failed");
}
