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This page holds a few example code-snippets for use in myana analysis. Compare with Pyana user examples to see how the same things can be done using the pyana analysis framework.

Display images from Princeton camera

Some variables are needed both in beginjob() and event() member functions. The myana solution is to declare them as global variables right after the necessary include-files.

#include <TH2I.h>

TH2I*        h_image;
static int   widthSxrRCI0;
static int   heightSxrRCI0;
static int   orgXSxrRCI0;
static int   orgYSxrRCI0;
static int   binXSxrRCI0;
static int   binYSxrRCI0;

In beginjob(), get configuration object and book histogram

 // Processing Princeton Config Data
  int fail = getPrincetonConfig( DetInfo::SxrEndstation, 0,
                                 widthSxrRCI0, heightSxrRCI0,
                                 orgXSxrRCI0, orgYSxrRCI0,
                                 binXSxrRCI0, binYSxrRCI0 );
  if ( fail == 0 ) {// success
    printf( "Get Princeton config for SxrRCI0: width %d height %d  org (%d,%d)  binX %d binY %d\n",
            widthSxrRCI0, heightSxrRCI0, orgXSxrRCI0, orgYSxrRCI0, binXSxrRCI0, binYSxrRCI0 );
  }

  // Book a histogram
  h_image = new TH2I("h_image","Princeton images (summed)",         // name and title
                      widthSxrRCI0,orgXSxrRCI0,widthSxrRCI0,        // nBinsX, xmin, xmax
                      heightSxrRCI0,orgYSxrRCI0,heightSxrRCI0);     // nBinsY, ymin, ymax

In event(), fetch data from Princeton camera for the current event. Add to histogram (which will hold the sum of all events). Note, we here use a root TH2 histogram. It's rather slow for images, so you may want to use some other display service...

  unsigned short* pixels;
  int fail = getPrincetonValue( DetInfo::SxrEndstation, 0, pixels);

  if ( fail == 0 ) {
    // Fill histogram from 2D array
    for(int irow=0; irow<heightSxrRCI0; irow++){
      for(int icol=0; icol<widthSxrRCI0; icol++){
        h_image->Fill(icol,irow,*pixels);
        pixels++; // go to the next pixel
      }
    }
  }

Once all events have been processed, you can display and/or store the histogram in myana's endjob() function.

  h_image->Draw();
  h_image->SaveAs("myana_princ_image.root");

  // 1D projections
  h_image->ProjectionX()->SaveAs("myana_princ_imageX.root");
  h_image->ProjectionY()->SaveAs("myana_princ_imageY.root");

At this point, you can open the histogram in root sessions and draw them there and interactively adjust display properties as needed.

> root
root > TFile f("myana_princ_image.root")
root > f.ls()
root > gStyle->SetPalette(1)
root > h_image->Draw()

Here's the plot:

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