How to use Root:

http://root.cern.ch/

"How to" page:
http://root.cern.ch/drupal/content/howtos
User's guide:
http://root.cern.ch/drupal/content/users-guide
Reference guide:
http://root.cern.ch/drupal/content/reference-guide

Run the Root:

root -l

Open a file:

TFile *_file0 = TFile::Open("..... .root")

File browser:

List the directories:

.ls
< directory name >.cd()

Print the tree:

< ntuplename >.Print()

Scan the tree:

< ntuplename >.Scan("< name of a Branch >.< name of a leaf >")

Make a new histogram:

TH1F *< name_of_the_histogram > = new TH1F ("< name >","",< #ofXaxis >,< #ofYaxis >,< #ofBins >);

Make a new canvas:

TCanvas *< c1 >=new TCanvas ("< name >","",1);

Draw a histogram:

< name of the tree in the file >.Draw("< name of a Branch >.< name of a leaf >")

2D histogram:

< name of the tree in the file >. Draw("< name of a Branch1 >.< name of a leaf1 >:< name of a Branch2 >.< name of a leaf2 >")

histogram with cut criteria:

< name of the tree in the file >.Draw("< name of a Branch1 >.< name of a leaf1 >,< name of a Branch2 >.< name of a leaf2 >< cut criteria>")

draw two histogram in one canvas:

< name of the tree in the file >.Draw("< name of a Branch1 >.< name of a leaf1 >")

< name of the tree in the file >.Draw("< name of a Branch2 >.< name of a leaf2 > ","","SAME")
e.g.:
tree.Draw("pelectron_1.tight: pelectron_1.loose ","pelectron_1.tight>-1")

Open an AOD file in root:

gSystem->Load("libFWCoreFWLite");
AutoLibraryLoader::enable();
TFile *_file0 = TFile::Open("rfio:/castor/cern.ch/user/........ .root")
TBrowser b

TChain:

Chain.C:
#include

void Chain(){
TChain tree("stopAnaMod/tree");
tree.AddFile("stopAnaNtuple_noselection_Chowder_00.root");
tree.Draw("event");
}

Save a histogram to .eps:

TCanvas *c1=new TCanvas ("","",1);

< name of the tree in the file >.Draw("< name of a Branch >.< name of a leaf >")

c1->SaveAs("< name >.eps");

Usage of MakeClass :

-- AnitaKapusi - 29 Jun 2009