Super-K Code Example 2: Making Histograms

This example is similar to the first, except that you will now create, fill, and output histograms, and use the PAW program to view them. You may want to have a look at the PAW tutorial first. This example will focus on histograms, but take a look at the ntuple section, too: "ntuples" are a very powerful feature of PAW.

Files for this example

Copy the following files from

/var/phy/project/hep/neutrino/work/schol/superk/examples

• example2.F: contains the source code for the program
• example2.sh: a shell script for running the program
• Recopy the Imakefile used for example1, which has had instructions for compiling example2 added to it.
• example2.kumac: a list of PAW commands which will plot the histogram you've created.

Take a look at the differences between example1.F and example2.F. You will see that several lines having to do with histograms have been added, which call HBOOK routines. HBOOK is a CERN library histogramming package, and the histograms it creates can be read by PAW.

• Before the file and event loops, the line

  call hbook1(100,'Example 2 charge',100,0., 100., 0.)

  creates in memory histogram no. 100 (the first argument), with 50 bins going from 0 to 100.
• For each hit in the loop,

   call hf1(100, qisk(ihcab(ihit)), 1.)

  "fills" the histogram with that hit's charge value. In other words, it increments the bin of the histogram corresponding to qisk for tube ihcab(ihit) by 1.
• At the end of the event and file loops, it outputs the histogram to a file using

   call hrput(0,'example2.hbk','N')

Compile and run this program in the same way as for example 1. You should get less output to the screen (because the print statements have been commented out), but you should get a file called example2.hbk created. This contains the histogram created and filled by the program.

Viewing the histogram

• Run the command "paw". You should get a command line interface.
• Enter the following lines:

  h/file 1 example2.hbk
  h/list
  h/plot 100
  

  The first line opens the file; the next lists the histograms in the file (there should be just one, no. 100); the last plots histogram 100. These commands are also written in example2.kumac, which is a PAW macro file. If you type exec example2 in the PAW command line, they will all be executed.

Stuff to try

After you've gotten this working and viewed the charge histogram, try some of the following. In the source code, change the histogram creation calls to:

• change the number of bins.
• change the x range plotted.
• create an additional hit time histogram with appropriate range.
• create a 2D histogram of charge vs time.

Also, inside PAW, try:

• getting a log scale.
• putting more than one plot on a page.
• superimposing more than one histogram.
• changing other display options.

Next: ntuples