TF ErrAna InClassLab
Start ROOT and Draw Histogram
Step 1
In this first lab your goal will be to start root and draw a histogram.
If you are on a Windows machine start the ROOT interpreter by double clicking on the Desctop icon which looks like a tree and says ROOT underneath it If you are on a Unix machine set the environmental variable ROOTSYS to point to the base subdirectory containing the ROOT files and start root with the command $ROOTSYS/bin/root. You can set the ROOTSYS environmental variable under the bash chell with the command
export ROOTSYS=path
where path identifies the location of the root base subdirectory. My ROOT base subdirectory is located at ~/src/ROOT/root so I would execture the following shell command
export ROOTSYS=~/src/ROOT/root
Step 2
Define a variable to contain the desired histogram
TH1F *Hist1=new TH1F("Hist1","Hist1",50,-0.5,49.5);
The above function "TH!F" has 5 parameters.
The first parameter "Hist1" create a name for the histogram. The second parameter gives the histogram a title. I usually set the name and title to the same variable name I use to store the histogram. This allows me to look up the variable name of the histogram when I double click on the histogram from the browser listing.
Hist1->Fill(10);
Hist1->Draw();