Users Guide 3.1d The ROOT User's Guide: Authors: René Brun/CERN, Fons Rademakers, Suzanne Panacek/FNAL, December, 2001 Damir Buskulic/Universite de Savoie/LAPP, Jörn Adamczewski/GSI, Marc Hemberger/GSI, Nick West/Oxford Comments to: [email protected] Editor: Suzanne Panacek/FNAL Special Thanks to: Philippe Canal/FNAL, Andrey Kubarovsky/FNAL Version 3.01 Up to version 3.1a, the User's Guide version numbers were independent of the software version numbers. With the release of ROOT 3.01 we adopted the convention to match the software version number. Hence the User's Guide version 3.01x documents ROOT version 3. All Users Guide versions 0.x document ROOT two. Maarten Ballintijn, Stephen Bailey, Damir Buskulic, Federico Carminati, Mat Dobbs, Rutger v.d. Eijk, Anton Fokin, Nick van Eijndhoven, George Heintzelman, Marc Hemberger, Christian Holm Cristensen, Jacek M. Holeczek, Stephan Kluth, Marcel Kunze, Christian Lacunza, Matthew D. Langston, Michal Lijowski, Peter Malzacher, Dave Morrison, Eddy Offermann, Pasha Murat, Valeriy Onuchin, Victor Perevoztchikov, Sven Ravndal, Reiner Rohlfs, Gunther Roland, Andy Salnikov, Otto Schaile, Alexandre V. Vaniachine, Torre Wenaus and Hans Wenzel, and many more Preface who have also contributed You all helped in making ROOT a great experience. Happy ROOTing! Rene Brun & Fons Rademakers Geneva, August 2000. In late 1994, we decided to learn and investigate Object Oriented programming and C++ to better judge the suitability of these relatively new techniques for scientific programming. We knew that there is no better way to learn a new programming environment than to use it to write a program that can solve a real problem. After a few weeks, we had our first histogramming package in C++. A few weeks later we had a rewrite of the same package using the, at that time, very new template features of C++. Again, a few weeks later we had another rewrite of the package without templates since we could only compile the version with templates on one single platform using a specific compiler. Finally, after about four months we had a histogramming package that was faster and more efficient than the well- known FORTRAN based HBOOK a histogramming package. This gave us enough confidence in the new technologies to decide to continue the development. Thus was born ROOT. Since its first public release at the end of 1995, ROOT has enjoyed an ever- increasing popularity. Currently it is being used in all major High Energy and Nuclear Physics laboratories around the world to monitor, to store and to analyze data. In the other sciences as well as the medical and financial industries, many people are using ROOT. We estimate the current user base to be around several thousand people. In 1997, Eric Raymond analyzed in his paper "The Cathedral and the Bazaar" the development method that makes Linux such a success. The essence of that method is: "release early, release often and listen to your customers". This is precisely how ROOT is being developed. Over the last five years, many of our "customers" became co-developers. Here we would like to thank our main co-developers and contributors: Masaharu Goto who wrote the CINT C++ interpreter. CINT has become an essential part of ROOT. Despite being 8 time zones ahead of us, we often have the feeling he is sitting in the room next door. Valery Fine who ported ROOT to Windows and who also contributed largely to the 3-D graphics and geometry packages. Nenad Buncic who developed the HTML documentation generation system and integrated the X3D viewer in ROOT. Philippe Canal who developed the automatic compiler interface to CINT. In addition to a large number of contributions to many different parts of the system, Philippe is also the ROOT support coordinator at FNAL. Suzanne Panacek who is the main author of this manual. Suzanne is also very active in preparing tutorials and giving lectures about ROOT. Further, we would like to thank the following people for their many contributions, bug fixes, bug reports and comments: Preface December 2001 - version 3.1d i ii December 2001 - version 3.1d Preface The Script Path ............................................................................. 25 Logon and Logoff Scripts ........................................................................... 25 Tracking Memory Leaks............................................................................. 26 Converting HBOOK/PAW files.................................................................. 26 Table of Contents 3 Histograms 29 The Histogram Classes................................................................................ 29 Creating Histograms ................................................................................... 30 Fixed or Variable Bin Size.......................................................................... 31 Bin numbering convention............................................................ 31 Re-binning .................................................................................... 32 Filling Histograms ...................................................................................... 32 Automatic Re-binning Option ...................................................... 32 Random Numbers and Histograms ............................................................. 33 Preface i Adding, Dividing, and Multiplying............................................................. 33 Projections .................................................................................................. 34 Table of Contents iii Drawing Histograms..................................................................... 34 Setting the Style............................................................................ 34 Draw Options.............................................................................................. 36 1 Introduction 1 Statistics Display......................................................................................... 37 The ROOT Mailing List................................................................................ 1 Setting Line, Fill, Marker, and Text Attributes........................................... 38 Contact Information ...................................................................................... 2 Setting Tick Marks on the Axis .................................................................. 38 Conventions Used in This Book ................................................................... 2 Giving Titles to the X, Y and Z Axis .......................................................... 38 The Framework............................................................................................. 3 The SCATter Plot Option ........................................................................... 39 What is a Framework? .................................................................... 3 The ARRow Option .................................................................................... 39 Why Object-Oriented?.................................................................... 4 The BOX Option......................................................................................... 39 Installing ROOT............................................................................................ 4 The ERRor Bars Options ............................................................................ 39 The Organization of the ROOT Framework ................................................. 6 The COLor Option...................................................................................... 40 $ROOTSYS/bin.............................................................................. 7 The TEXT Option....................................................................................... 41 $ROOTSYS/lib............................................................................... 7 The CONTour Options................................................................................ 42 $ROOTSYS/tutorials...................................................................... 9 The LEGO Options ..................................................................................... 43 $ROOTSYS/test ............................................................................. 9 The SURFace Options ................................................................................ 44 $ROOTSYS/include ..................................................................... 10 The Z Option: Display the Color Palette on the Pad................................... 45 $ROOTSYS/<library>.................................................................. 10 Setting the color palette ................................................................ 45 How to Find More Information................................................................... 11 Drawing a Sub-range of a 2-D Histogram (the [cutg] Option) ................... 46 Drawing Options for 3-D Histograms......................................................... 46 2 Getting Started 13 Superimposing Histograms with Different Scales ...................................... 47 Making a Copy of an Histogram................................................................. 48 Start and Quit a ROOT Session .................................................................. 13 Normalizing Histograms............................................................................. 48 Exit ROOT.................................................................................... 15 Saving/Reading Histograms