#include <iostream.h>


void graph_test() {


// open text file
ifstream infile;
infile.open("./velocity_table.txt", ifstream::in);

Int_t numoflines=0;
Float_t radius,velocity,vel_error;

TGraphErrors * v_r_1 = new TGraphErrors();


// read the data from the file and store it in the TGraphErrors:
// first column -> radius
// second column -> velocity
// third column -> vel_error

while(!infile.eof()) {
	numoflines++;
		
	infile >> radius;
	infile >> velocity;
	infile >> vel_error;
	
		
	if (infile.eof()) break;
	
	v_r_1->Set(numoflines);
	v_r_1->SetPoint(numoflines-1,radius,velocity);
	v_r_1->SetPointError(numoflines-1,0.,vel_error);
	
}

infile.close();

	
v_r_1->SetMarkerStyle(kFullCircle);						
//v_r_1->SetMarkerSize(0.8);


TMultiGraph *v_r = new TMultiGraph();

v_r->Add(v_r_1);
v_r->Draw("AP");

}