root

April 22, 2023 ROOT Day1 1

ROOTAn Object Oriented Data

Analysis Framework

Day 1


The Early ROOT Team


The ROOT Web Pages

http://root.cern.ch General Information and News

Download source and binaries

HowTo’s & tutorials

User Guide & Reference Guide

Roottalk mailing list & Forum

Savannah bug reporting and [email protected]


Acknowledgements

Suzanne Panacek (Fermilab) Philippe Canal (Fermilab)

For their help in developing this course


Class Schedule - Day 1 Overview of the ROOT Framework GUI basics Command line basics Finding Information (class

reference guide)

Getting started with the exercises


Class Schedule - Day 2 ROOT commands and CINT Discuss exercises Functions and fitting Building ROOT Trees Reading Trees Using Trees in Analysis


Class Schedule - Day 3 Copying Trees Chain of trees Adding your class to ROOT

With the Interpreter With a compiler (Shared Library) With ACLiC

Rootcint ROOT I/O details Remote I/O


ROOT Overview What is ROOT What about PAW Concepts: Object Oriented Design,

Frameworks Services and Utilities Libraries Physical Organization


Prehistory In the beginning there was PAW

HBOOK ZEBRA KUIP COMIS SIGMA

Mini/Micro-DST analysis was done using Ntuples Ntuples are basically simple tables Only basic types No data structures No cross reference between Ntuples Successful because simple and efficient

Dead-end No way to grow to more complex data structures Difficult to extend Expensive to maintain Too many languages: Fortran, KUIP, SIGMA


Main Goals for New System

Being able to support full data analysis chain Raw data, DSTs, mini-DSTs, micro-DSTs

Being able to handle complex structures Complete objects Object hierarchies

Support at least the PAW data analysis functionality Histogramming Fitting Visualization

Only one language C++

Better maintainable Use OOP

Make the system extensible Use OO framework technology


ROOT in a Nutshell The ROOT system is an Object Oriented framework

for large scale data handling applications Written in C++ Provides, among others,

an efficient data storage and access system designed to support structured data sets (PetaBytes)

a query system to extract data from these data sets a C++ interpreter advanced statistical analysis algorithms (multi dimensional

histogramming, fitting, minimization and cluster finding) scientific visualization tools with 2D and 3D graphics an advanced Graphical User Interface

The user interacts with ROOT via a graphical user interface, the command line or scripts

The command and scripting language is C++, thanks to the embedded CINT C++ interpreter, and large scripts can be compiled and dynamically loaded


ROOT: An Open Source Project The project is developed as a

collaboration between: Full time developers:

10 people full time at CERN 2 developers at FermiLab 1 developer in Japan (Agilent Technologies) 2 developers at MIT

Large number of part-time contributors Several thousand users giving feedback,

comments, bug fixes and many small contributions

An Open Source Project, source available under the LGPL license


ROOT Development Process We follow an Open Source development model

“Release early, release often” Major releases 3-4 times per year Minor releases every 2-3 weeks Daily/nightly builds + regression testing +

benchmarking (rootmarks) “Let user feedback drive the development”

Bug reporting system Roottalk mailing list Annual workshop Open cvs repository Let users become developers


Object Oriented Concepts

Members: a “has a” relationship to the class.

Inheritance: an “is a” relationship to the class.

Class: the description of a “thing” in the system Object: instance of a class Methods: functions for a class

TObject

Segment Track Vertex

MomentumMassSquare

MeanCharge

EventIsA

HasAHasA

HasA

HasAHasAHasA


A Frameworkprovides utilities and services


ROOT's Services and Utilities Data analysis and visualization tools Histogramming and Fitting 2D and 3D graphics, Postscript, PDF, LateX Geometrical modeller Object persistency and Trees PROOF parallel query engine Collection Classes Run Time Type Identification Online services User Interface

GUI: Browsers, Panels, Tree Viewer Command Line interface: C++ interpreter CINT Script Processor (C++ compiled C++ interpreted)


Calling API vs Sub-classing API

Program usingcalling API

Class

Class Amethod B

Class Yvirtual method Z

Framework

Class

ClassClass

Class newYvirtual method Z

Program usingsub-classing API

calls

inherits


ROOT Library Structure ROOT libraries are a layered structure The CORE classes are always required (support for RTTI,

basic I/O and interpreter) The optional libraries (you load only what you use).

Separation between data objects and the high level classes acting on these objects. Example, a batch job uses only the histogram library, no need to link histogram painter library

Shared libraries reduce the application link time Shared libraries reduce the application size ROOT shared libraries can be used with other class

libraries Shared libraries are mostly loaded via the plug-in manager


The ROOT Libraries Over 1000

classes

1,350,000 lines of code

CORE (12 Mbytes)

CINT (2 Mbytes) Green libraries

linked on demand via plug-in manager (only a subset shown)


Three User Interfaces GUI

windows, buttons, menus

Command lineCINT (C++ interpreter)

Macros, applications, libraries (C++ compiler and interpreter)


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.


PAW to ROOT File Conversion Get the example PAW file from

ftp://root.cern.ch/root/exercises.tar.gz exercises_files/day1/toyz.rz

At the system prompt type

> 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.html


A Data Analysis & Visualization Tools


Graphics: 1,2,3-D functions


Histograms


Full LateX support

on screen and

postscript

TCurlyArcTCurlyLineTWavyLine

and other building blocks for Feynman diagrams

Formula or

diagrams can beedited

with the mouse


Alice 3 million nodes


ROOT Overview Summary Concepts: Object Oriented Design,

Frameworks Services and Utilities Libraries Physical Organization PAW Compatibility Some Visual Examples


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


GUI Basics

Display the browser TBrowser b;

Start root> root

Quit root (just in case)

root[0] .q


Displaying a Histogram

Display a histogram The Canvas

Open the ROOT fileBrowse the file


Basic Navigation by Clicking

Left Click select the object drag the object resize the object

Right Click context menu class::name methods

Middle Click activate canvas pop pads freezes event status bar


The Editor Panel The Event Status

The Editor Panel

Adding Error barsChanging colorsStyles


The Editor Panel

SlidersRebining


Fitting, Coloring, and Zooming

Adding a gaussian fit Coloring the histogram Zooming/unzooming


Adding Objects to the Canvas

The Editor Adding an Arrow Adding Text


Adding Another Pad Add a Pad Select the new

Pad Draw a histogram Add a title for the

axis


Modifying the Statistics The Canvas in the

Browser Setting the (7)

statistics options default = 0001111


Dividing the Canvas Create a new Canvas Divide it in 2 Draw two histograms.

1. Lego plot2. LogY


1-D Drawing OptionsAny object in the canvasis clickable and editable


2-D Drawing Options


2-D Drawing Options

All these plots can be rotated with the mouse


2-D Drawing Options

Same outputon the screen and with

vector Postscript


THStack Examples


Filling with String Variables


Command Line Basics Use up and down arrows to

recall commands $HOME/.root_hist

Use emacs commands to navigate


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 myTree;1 Example ROOT tree KEY: TH1F totalHistogram;1 Total Distribution KEY: TH1F mainHistogram;1 Main Contributor KEY: TH1F s1Histogram;1 First Signal KEY: TH1F s2Histogram;1 Second Signal


Plotting a Variable Plot a variable

root [] myTree->Draw("xs1")

Where did myTree come from? ROOT executed an implicit gROOT->FindObject("myTree")

And now.. root[] f.ls() … OBJ: TTree myTree Example ROOT tree: 0 KEY: TTree myTree;1 Example ROOT tree


The ROOT File

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


The ROOT Tree Stores large quantities of same

class objects: Optimize disk space Optimize access speed Had analysis methods (TTree::Draw())

TNtuple is a TTree limited to floating point numbers.

More details later …


Fitting To add a Gaussian Fit

root [] htemp->Fit("gaus")

Where did htemp come from?automatically generated

histogram by the TTree::Draw() command.


Color and Error Bars To add color

root [] htemp->SetFillColor(9) See pg. 134 of the Users Guide for color

index Or in any Canvas choose View:Colors

Drawing Error Barsroot[] htemp->Draw("E1,same")

Many Draw Options See the User's Guide


Command Line Basics Open and browse a file Drawing histograms Adding a Fit Adding Error bars Adding Color


Class Reference Guide Find the class in the index, for

example TH1. Class Inheritanceclass TH1 : public TNamed, public TAttLine, public

TAttFill, public TAttMarker Class Description Private members Public methods Code

http://root.cern.ch/root/roottalk/AboutRootTalk.html

mailto:[email protected]

mailto:[email protected]


Finding Examples The ROOT Tutorials:

http://root.cern.ch/root/Tutorials.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

http://root.cern.ch/



http://root.cern.ch/root/html/ClassIndex.html

http://root.cern.ch/root/Tutorials.html

http://root.cern.ch/root/roottalk/AboutRootTalk.html


Summary Overview of ROOT GUI Basics Command line basics Using the Class reference

guide PAW to ROOT conversion


Exercise Overview Session A

Use ROOT command line Write a named and un-named script Use the GUI to create objects and change their attributes Save your canvas to a PostScript file Fit a graph

Session B Fit and rotate a histogram Use the Object Browser and the Tree Viewer Make a profile and contour graphs Build an event list from a cut Fill a histograms with random numbers Use ACLiC


Exercise Session C Session C:

Study an example analysis from H1 at DESY Learn about the TTree::MakeSelector() method to

automatically create a class that loops over each entry in a tree.

Save and retrieve a canvas to and from a ROOT file Compute the integral of a histogram Compute the integral of a function within a range


Installing ROOT Go to ROOT web page and download

the latest version of ROOT Install according to description

Set shell variablesROOTSYS, LD_LIBRARY_PATH and PATH

Make sure you can do: root root [0] .q


Getting Started with the Exercises

Find the exercises on line at:

ftp://root.cern.ch/root/exercises.tar.gz

Today Session A.

root

Documents

data analysis chainraw

root commands

nutshellthe root system

efficient data storage

object oriented framework

access system

source available

time developers