Documentation on zeesim

Task: zeesim
Purpose: Test reliability of Zeeman splitting errors
Categories: profile analysis

  Estimate the reliability of Zeeman error estimates for spatial 
  summing or averaging.    This is generally essential for spatial
  summing, and possibly needed for spatial averaging when eta is 
  of the order of unity.

  Program in four logical sections
  1)  Read in data
  2)  Fit data and get estimates of noise free spectra
  3)  Find the FFT of the beam
  4)  Simulate by adding correlated noise and refitting

Key: iin
        Input I cube (vxy order). Wild card expansion supported.  
        No default.

Key: vin
        Input V cube (vxy order). Wild card expansion supported. 
        No default.

Key: beam
        The beam of the observation.  Wild card expansion supported.  
        Not needed for AVEOP=`a'

Key: mode
        This is a character string that determines the algorithm used 
        in the fitting process. It consists of several flags, which 
        can be:
          m Use maximum likelihood technique.
          l Include a leakage term in the fitting.
          2 Use a two sided derivative estimate.
          x Perform extra checks for better solutions when using the 
            maximum likelihood technique.
          d Debiased least squares estimate.
        The default is ' ' i.e., least squares and 1.

Key: aveop
        `a' for averaged spectrum in window, `s' for summed spectra
        Summed computational load is orders of magnitude greater than for 
        averaged spectra.  'h' for hybrid of averaging and summing.
        Default is `a'.  The hybrid is the same as `s', except when 
        fitting the simulated spectra, whereupon the spectra are first
        averaged for each window.

Key: chan
        Channel range. Default is all channels.

Key: freq
        Frequency (GHz) for conversion of channel splitting to B field.

Key: blc
        Bottom left corner of spatial region to examine. Default is (1,1).

Key: trc
        Top right corner of spatial region to examine. Default is all
        of image.

Key: bin
        Binning widths for all three (v,x,y) dimensions. Default = 1. 
        This keyword enables each region (spectral and spatial) to 
        be binned up before fitting.  It's as if you had observed
        with lower resolution.  Spatial binning is of no use if
        you are using spatial averaging.

Key: split
        Splitting (split to unsplit in channels) to use for calculation
        of hatV and all simulation (i.e., don't use actual splitting
        as predicted by fitting algorithm when generating V spectra.

Key: nruns
        The number of simulation runs to undertake.   If 0, then just
        the initial fits are done.  Default is 0.

Key: infile
        File containing a list of windows.  If this file specified,
        blc and trc are ignored.  Should be in format:
          NWIN
          I XCEN YCEN XOFF YOFF
        And there are nwin of these lines.  XOFF and YOFF define the
        box half-sizes from their specified centres, XCEN and YCEN.
        You can leave off XOFF and YOFF and they will default to 2
        All units are pixels.

Key: log
       If NRUNS = 0
          One value which is a root file name, appended to which is
         the box number as specified in the INFILE (or = 1 for
         a box specified with BLC and TRC).   These files contain
         the fitted results for each window.   The files are opened
         in APPEND mode.

       If NRUNS   0
         Two values.  The first is a root file name, appended to which 
         is the box number as specified in the INFILE (or = 1 for
         a box specified with BLC and TRC).   These files contain the
         results for each simulation with a cumulative fiddle factor
         worked out.  The first line is the initially fit results
         before simulation.
         The second value is a file containing a statistical summary
         of the final results of the simulations from all windows, 
         including the initially fit results before simulation began.

Key: nran
        Throw away NRAN random numbers before starting.  Use this to 
        continue a set of simulations with different random numbers.