Basic Information 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.

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