ROOT

1
ROOT

• An object oriented HEP analysis framework.

Day 1
2
ROOT User's Workshop

• Fermilab
• June 13-15, 2001
• http//patwww/root/root2001/

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The ROOT Team
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ROOT contacts at Fermi

• Philippe Canal , x2545 pcanal_at_fnal.gov
• Suzanne Panacek, x8334 spanacek_at_fnal.gov
• Jeff Kallenbach, x2210
• jeffk_at_fnal.gov

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Mailing Lists

• the ROOT mailing list
• roottalk_at_root.cern.ch
• archives
• http//root.cern.ch/root/roottalk/AboutRootTalk.ht
  ml
• Fermilab mailing list
• about-root_at_fnal.gov
• archives
• http//listserv.fnal.gov/archives/about-root.html

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Class Schedule

• Day 2
• Monday, 3/19/01  9AM 11AM in EOC Large Class
  Room
• Day 3
• Tuesday, 3/20/01 1PM- 3PM in EOC Large Class
  Room

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Class Schedule - Day 1

• Overview of the ROOT Framework
• GUI basics
• Command line basics
• Finding Information (class reference guide)
• Getting started with the exercises

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Class Schedule - Day 2

• Root Commands and CINT
• Discuss Exercises
• Functions and Fitting
• The Tree Viewer

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Class Schedule - Day 3

• Building ROOT Trees
• Reading Trees
• Using Trees in Analysis
• TTree-gtDraw
• TTree-gtMakeClass
• Chains
• Exercise discussion
• How to add your Own Class
• With the Interpreter
• With the compiler (shared library)
• With ACLiC

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ROOT Overview

• What about PAW
• Concepts Object Oriented Design, Frameworks
• Services and Utilities
• Libraries
• Physical Organization

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Differences from PAW

• Regular grammar (C) on command line
• Single language (compiled and interpreted)
• Object Oriented (use your class in the
  interpreter)
• Advanced Interactive User Interface
• Well Documented code. HTML class descriptions for
  every class.
• Object I/O including Schema Evolution
• 3-d interfaces with OpenGL and X3D.

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PAW to ROOT File Conversion

• Get the example PAW file from http//www-pat.fnal
  .gov/root/examples/toyz.rz
• At the system prompt type
• gt h2root toyz.rz toyz.root
• Once you've done the conversion, you can then
  start a ROOT session and open toyz.root
• Also see http//root.cern.ch/root/HowtoConvert.ht
  ml

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Object Oriented Concepts

• Class the description of a thing in the
  system
• Object instance of a class
• Methods functions for a class

• Members a has a relationship to the class.
• Inheritance an is a relationship to the class.

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A Framework
provides utilities and services.
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ROOT's Services/Utilities

• Histogramming and Fitting
• Graphics (2D, 3D)
• I/O to file or socket specialized for
  histograms, Ntuples (Trees)
• Collection Classes and Run Time Type
  Identification
• User Interface
• GUI Browsers, Panels, Tree Viewer
• Command Line interface C interpreter CINT
• Script Processor (C compiled ? C
  interpreted)

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The Libraries

• Over 350 classes
• Core
• CINT
• Libraries loaded at startup Hist, Tree
• Libraries loaded when needed HistPainter,
  TreePlayer,
• Special purpose libraries EG, Physics

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The Framework Organization
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Three User Interfaces

• GUIwindows, buttons, menus
• Root Command lineCINT (C interpreter)
• Macros, applications, libraries (C compiler and
  interpreter)

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ROOT Overview Summary

• PAW
• Concepts Object Oriented Design, Frameworks
• Services and Utilities
• Libraries
• Physical Organization

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GUI Basics

• Browsing and opening files
• Drawing histograms
• Right click, left click, middle click
• Draw Panel
• Fit Panel
• Adding Color and Zooming
• Adding text and other objects
• Dividing the canvas
• Setting the log scale

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GUI Basics
Start root gt root Quit root (just in case)
root0gt.q

• Display the browser
• TBrowser b

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Displaying a Histogram
Open the root file Browse the file

• Display a histogram The Canvas

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Basic Navigation by Clicking

• Left Click
• select the object
• drag the object
• resize the object
• Right Click
• context menu
• classname
• methods
• Middle Click
• activate canvas
• freezes event status bar

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The Draw Panel

• The Event Status

The Draw Panel Adding Error bars Slider Defaults
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Fitting, Coloring, and Zooming

• Adding a gaussian fit
• Coloring the histogram
• Zooming/unzooming

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Adding Objects to the Canvas

• The Editor
• Adding an Arrow
• Adding Text

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Adding another Pad

• Add a Pad
• Select the new Pad
• Draw a histogram
• Add a title for the axis

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Modifying the Statistics

• The Canvas in the Browser
• Setting the (7) statistics options
• default 0001111

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Dividing the Canvas

• Create a new Canvas
• Divide it in 2
• Draw two histograms.
• 1. Lego plot
• 2. LogY

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Command Line Basics

• Use up and down arrows to recall commands
• HOME/.root_hist
• Use emacs commands to navigate

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Open a File

• Open a file for reading
• root TFile f("Example.root")
• Look at the contents of the file
• root f.ls()
• TFile Example.root ROOT file
• TFile Example.root ROOT file
• KEY TTree myTree1 Example ROOT tree
• KEY TH1F totalHistogram1 Total
  Distribution
• KEY TH1F mainHistogram1 Main Contributor
• KEY TH1F s1Histogram1 First Signal
• KEY TH1F s2Histogram1 Second Signal

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Plotting a Variable

• Plot a variable
• root myTree-gtDraw("xs1")
• Where did myTree come from?
• ROOT executed an implicit gROOT-gtFindObject("myTr
  ee")
• And now..
• root f.ls()
• OBJ TTree myTree Example ROOT tree 0 KEY
  TTree myTree1 Example ROOT tree

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The ROOT File

• A TFile is a directory structure like UNIX
• Object in Memory (OBJ) Object on Disk (KEY)

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The ROOT Tree

• Stores large quantities of same class objects
• Optimize disk space
• Optimize access speed
• Had analysis methods (TTreeDraw)
• TNtuple is a TTree limited to floating point
  numbers.
• More details later

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Fitting

• To add a Gaussian Fit
• root htemp-gtFit("gaus")
• Where did htemp come from?
• automatically generated histogram by the
  TTreeDraw command.

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Color and Error Bars

• To add color
• root htemp-gtSetFillColor(9)
• See pg. 134 of the Users Guide for color index
• Or on any Canvas choose ViewColors
• Drawing Error Bars
• root htemp-gtDraw("E1,same")
• Many Draw Options
• See the User's Guide

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Command Line Basics

• Open and browse a file
• Drawing histograms
• Adding a Fit
• Adding Error bars
• Adding Color

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Where to Find Information

• The ROOT Home http//root.cern.ch
• Talks and publications on ROOT
  http//root.cern.ch/root/Publications.html
• To get information on a specific class
  http//root.cern.ch/root/html/ClassIndex.html

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Class Reference Guide

• Find the class in the index, for example TH1.
• Class Inheritance
• class TH1 public TNamed, public TAttLine,
  public TAttFill, public TAttMarker
• Class Description
• Private members
• Public methods
• Code

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Finding Examples

• The ROOT Tutorials http//root.cern.ch/root/Tutor
  ials.html
• The ROOT How To's http//root.cern.ch/root/Howto.
  html
• For on-line help for a particular topic it's very
  useful to use their facility to search the ROOT
  site. http//root.cern.ch/root

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More Information

• To subscribe to roottalk http//root.cern.ch/root
  /roottalk/AboutRootTalk.html
• To submit a bug reporthttp//pcroot.cern.ch/root
  -bugs
• About ROOT at Fermi about-root_at_fnal.gov
• http//ods.fnal.gov/ods/root-eval/current/
• To subscribe to the about-root mailing list send
  mail to listserv_at_fnal.gov with the body of the
  email subscribe about-root email_at_addresses.

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Summary

• Overview of ROOT
• GUI Basics
• Command line basics
• Using the Class reference guide
• PAW to ROOT conversion

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Getting started with the Exercises

• Go to http//patwww.fnal.gov/root/class/Setup.htm
  for setup instructions using Reflection and ssh
  on fcdfsgi2 and d0mino and minos1.
• Find the exercises on line at
• http//patwww.fnal.gov/root/class/exercises.htm