Introduction of ROOT

Yao

ROOT Development

• In the mid 1990's, René Brun and Fons Rademakers, they had lead successful projects such as PAW, PIAF, and GEANT .

• They knew the twenty-year-old FORTRAN libraries had reached their limits, could not scale up to the challenges offered by the Large Hadron Collider.

• At the same time, computer science had made leaps of progress especially in the area of Object Oriented Design (OOD).

What is ROOT ?

Object-Oriented Design (OOD)

• Modularity• Reusability• Extendibility• Maintenance• Etc…

• Smalltalk: Smalltalk-80• C based : objective-C , C++ , JAVA , C# • LISP based : Flavors , XLISP , LOOPS ,CLOS • PASCAL based : Object Pascal , Turbo Pascal ,

Eiffel , Ada 95

CINT

• CINT is a command line C/C++ interpreter.• The syntax is a bit more forgiving than either

language.

Interpreted languages :• BASIC , Lisp , Perl , Scheme , Python , Ruby ,

Tcl and Tk , Unix Shell , JavaScript , PHP , VBScript

• ROOT is an object-oriented framework aimed at solving the data analysis challenges of high-energy physics ,

• it provides a large selection of HEP specific utilities such as histograms and fitting.

• 2D Graphics, 3D Graphics , etc.

Why do we use ROOT ?

histogram

histograms and fitting

2D Graphics

3D Graphics

Setting the Environment Variables[shyao@ipas012 ~] $ export SOFT="${HOME}/local"[shyao@ipas012 ~] $ export ROOTSYS="${SOFT}/root"[shyao@ipas012 ~] $ export PATH="${SOFT}/root/bin:${PATH}"[shyao@ipas012 ~] $ export LD_LIBRARY_PATH="${SOFT}/root/lib/root:$

{LD_LIBRARY_PATH}”

~/.bashrc

Please note: the syntax is for bash.

How to use ROOT ?

Start and Quit a ROOT Session [shyao@ipas012 ~] $ root**************************************** ** W E L C O M E to R O O T ** ** Version 5.27/02 26 April 2010 ** ** You are welcome to visit our Web site ** http://root.cern.ch ** ****************************************

ROOT 5.27/02 (trunk@33229, Apr 27 2010, 11:38:29 on linux)

CINT/ROOT C/C++ Interpreter version 5.17.00, Dec 21, 2008Type ? for help. Commands must be C++ statements.Enclose multiple statements between { }.root [0] .q[shyao@ipas012 ~] $

help[shyao@ipas012 ~]$ root -?Usage: root [-l] [-b] [-n] [-q] [dir] [[file:]data.root] [file1.C ... fileN.C]Options: -b : run in batch mode without graphics -n : do not execute logon and logoff macros as specified in .rootrc -q : exit after processing command line macro files -l : do not show splash screen dir : if dir is a valid directory cd to it before executing

command line

root[0] 1+sqrt(9)(const double)4.00000000000000000e+00root[1] for (int i = 0; i<4; i++) cout << "Hello " << i << endlHello 0Hello 1Hello 2Hello 3root[2] .q

histogramvoid fith() { // filename double tmp; ifstream fin("./data/rr.txt"); int i=0;

TCanvas *c1 = new TCanvas("c1","fitting Histogram",200,10,700,500); TH1D *h1 = new TH1D( "h1", "hist1", 20, 0, 10 );

while(!fin.eof()){ fin>>tmp; h1->Fill( tmp*1000000. ); } fin.close();

h1->SetTitle("muon lifetime"); h1->SetXTitle("10^{-6}s"); h1->SetYTitle("count"); //******** h1->Draw("E");C1->Print();}

Do not need to include header file that root provide.

Run a script

[shyao@ipas012 ]$ root fith.Corroot [0] .x fith.C

fittingTF1 *t1 = new TF1("t1","[0]+[1]*exp(-x/[2])",0,bin);t1->SetParNames("a","b","lifetime");t1->SetParameter(0,6);t1->SetParLimits(0,0,10);t1->SetParameter(1,1);t1->SetParameter(2,2.2);h1->Fit("t1");

[shyao@ipas012 ]$ root fith.CNO. NAME VALUE ERROR SIZE DERIVATIVE 1 a 2.66609e+00 1.56321e+00 3.68519e-04 4.12958e-04 2 b 1.48634e+02 9.03901e+00 1.18599e-02 1.96484e-05 3 lifetime 2.26596e+00 1.82994e-01 1.49850e-04 1.42577e-03

Scatter Diagramvoid graph() { TCanvas *c1 = new TCanvas("c1","A Simple Graph Example",200,10,700,500);

const Int_t n = 20; Double_t x[n], y[n]; for (Int_t i=0;i<n;i++) { x[i] = i; y[i] = sin(i*0.5); } gr = new TGraph(n,x,y); //****** gr->Draw("AP*");

c1->Update(); c1->Modified();}

[shyao@ipas012 code]$ root graph.C

gr->SetLineColor(2);gr->SetLineWidth(4);gr->SetMarkerColor(4);gr->SetMarkerStyle(21);gr->SetTitle("a simple graph");gr->GetXaxis()->SetTitle("X title");gr->GetYaxis()->SetTitle("Y title");gr->Draw("ACP*");

2D Graphicsvoid graph2d(){ TCanvas *c = new TCanvas("c","Graph2D example",0,0,700,600); Double_t x, y, z, P = 6.; Int_t np = 200; TGraph2D *dt = new TGraph2D(); TRandom *r = new TRandom(); for (Int_t N=0; N<np; N++) { x = 2*P*(r->Rndm(N))-P; y = 2*P*(r->Rndm(N))-P; z = (sin(x)/x)*(sin(y)/y)+0.2; dt->SetPoint(N,x,y,z); } gStyle->SetPalette(1); dt->Draw("surf1");

}