#include "TF1.h"
#include "TH2F.h"
#include "TPad.h"

Double_t droite(Double_t *x, Double_t *par);

void TestGetX(Int_t npx=100)
{
	//Test inversion of linear function with TF1::GetX.
	//Use npx argument to change precision of inversion (calls SetNpx(npx)).
	
	TF1* func = (TF1*)gROOT->FindObject("my_func");
	if(!func) func = new TF1("my_func", droite, 0, 5000, 2);
	func->SetNpx(npx);
	func->SetParameters(10.,10.);
	//histo pour la fonction inverse
	TH2F* h2 = (TH2F*)gROOT->FindObject("h2");
	if(!h2) h2 = new TH2F("h2","x vs. y",1000,0,6000,500,0,500);
	else h2->Reset();
	//remplit l'histo
	for(Double_t lite=0.;lite<=6000.;lite+=6.) h2->Fill(lite, func->GetX(lite));
	if( gPad ) gPad->Modified();
	else h2->Draw("box");
	gPad->Update();
}