Subject: Common structure / function for spectra


  Dear all,

  as second part of my actions from our meeting, here are
some propositions to handle spectra. Your comments are very
welcome, it is actually a bit disconcerting to have resounding
silence on these mails - some of you should be affected, for 
the last mail (events) even more than for the current.

  Based on the existing OGIP/ISDC data structures for spectra
I'd propose the following generic structure:

typedef struct {
    char           spectrumID[DAL_MED_STRING];      /* -> ROWID of PHA II */
    unsigned short channel[J_NUM_PI_BINS];
    double         rate[J_NUM_PI_BINS];
    double         errStat[J_NUM_PI_BINS];
    double         errSys[J_NUM_PI_BINS];
    int            quality[J_NUM_PI_BINS];
    double         exposure;
    double         timeElapsed;
    double         timeOn;
    double         deadtimeCorrectionFactor;
    double         timeFirst;
    double         timeLast;
    Event_type     eventType;  /* e.g. JEMX_FULL, JEMX_REST */
} JEMXspectrum;

Note that one could also include these things in higher level structs:

typedef struct {
   ...
   double          RA;
   double          Dec;
   JEMXspectrum    spectrum;
   ...
} JEMXsource;

which you could then access as in: (src[i]).spectrum.exposure=summedExposure;
if defined src as an array of JEMXsource.


  The question is for me what kind of functions one would need
to go with that. Clearly a useful function would write out a 
spectrum to a table. But would we rather have a function that
takes a JEMXspectrum and additional parameters, e.g., for the
source info, or functions written around higher level structs
still?

  Also I could imagine functions to:
* Initialize a spectrum / an array of spectra to zero
* Add N selected, contigous events to a spectrum
* Do basic mathematical operations on two spectra

  Any more ideas?

  Regards,
  Peter