UVDIST


UVDIST  plots  the  amplitudes  in  a  MERGE-format   dataset   versus
uv-distance   (projected  baseline,  or  radius  from  origin  in  the
uv-plane).  One dot or error bar is  plotted  for  each  (non-deleted)
data  point.   A  simple  circularly-symmetric  Gaussian  model may be
plotted on the graph.

     The following example produces a printer plot from a  MERGE  file
called [TJP.MAR79]1633.MRG:

$ UVDIST
INPUT = "[TJP.MAR79]1633.MRG"
PLOTFILE = "UVDIST.PLT/PRINTR"
XAXIS = "UVKM"
FLUX = 1.24  FWHM = 0.35
/
$ 


Parameters

End  the  list  of  parameters  with  a  slash  (/)   or   end-of-file
(control-Z).  The following parameters can be specified:

INPUT = "filename" :  the filename of  the  input  MERGE-format  file.
          This parameter must be specified.

PLOTFILE = "device/type" :  any valid  graphics  device  specification
          may be supplied, e.g., "TTA4:/TEK" for a Tektronix terminal,
          "/G" for a Grinnell, "/VT" if  your  terminal  is  a  VT125,
          "UVDIST.PLT/VERS"  for  a Versatec-format file.  The default
          destination for the plot file is the  logical  name  TEKTERM
          which is defined in the VLB LOGIN.COM file.

XAXIS = "option" :  parameter XAXIS controls  the  formatting  of  the
          horizontal  axis  of  the graph.  Allowed values are XAXIS =
          "UVDIST" for uv-distance (projected baseline) in millions of
          wavelengths,  XAXIS  = "UVMETERS" for uv-distance in meters,
          XAXIS = "UVKM" for uv-distance  in  kilometers,  "UVPA"  for
          position  angle  in  the  uv-plane,  or  "PROJ" for baseline
          projected onto position angle BAPA.  The  value  string  (in
          quotation  marks)  can be in upper or lower case, and can be
          abbreviated to uniqueness (3 letters).  Unrecognised  values
          are treated as "UVDIST", the default value.

YAXIS = "option" :  the only allowed  value  for  YAXIS  is  "AMP"  at
          present.

XRANGE = min,max :  two values specify the range of the x-axis  (units
          are  millions of wavelengths, meters or kilometers depending
          on the value of XAXIS); if XRANGE is not  specified,  values
          will be chosen to include all the data.

UVDIST                                                            Page 2


YRANGE = min,max :  two values specify the range of the y-axis  (units
          are  Jy if the dataset has been calibrated, or dimensionless
          correlation  coefficient  otherwise);  if  YRANGE   is   not
          specified, values will be chosen to include all the data.

MARK = n :  set the symbol to be used for plotting  each  point.   The
          default  is -1, which gives a single dot.  See documentation
          on  the  graphics  package  (PGPLOT)  for  the  full  symbol
          repertoire.

ERRORS (no value) :  if specified, vertical error bars (+/-  1  sigma)
          are  drawn  through  each point; if both MARK and ERRORS are
          specified, the marker appears in the  middle  of  the  error
          bar.

FLUX = f1,f2 :  if specified, a circularly  symmetric  Gaussian  model
          consisting  of 1 or 2 components is computed and its profile
          plotted on the graph.  FLUX specifies the flux  density  (in
          Jy) of the 1 or 2 components.

FWHM = d1,d2 :  specifies the FWHM  im  milliarcsec  of  the  1  or  2
          Gaussian model components; ignored if FLUX is not specified.
          Default is FWHM = 0,0.

LINEWIDTH = n :  set the linewidth for the plotter.  1 is  recommended
          for  all  devices  except  Versatec;  2  or  3 may give good
          results on Versatec.

DOTSIZE = n :  set the linewidth to be used for plotting  each  point;
          if  DOTSIZE  is  not  specified,  the  default value is that
          specified for LINEWIDTH.

FONT = n :  set the font to be used for the text annotating  the  plot
          [1=default, 2=roman, 3=italic, 4=script].

BAPA = angle:  used in conjunction with XAXIS='PROJ',  this  specifies
          the projection position angle.


XAXIS options

XAXIS='UVDIST', 'UVMETERS', or 'UVKM':  x = sqrt(u**2 + v**2).

XAXIS= 'UVPA':  position angle of the baseline.

XAXIS='PROJ':  the baseline is projected along  a  specified  position
angle  given  by parameter BAPA.  This is useful if the source has (or
is  suspected  of  having)  a  well=defined  axis  and  the  data  are
insufficient for hybrid mapping.  Also, it can be useful in displaying
that the structure found in a map shows up  explicitly  in  the  data,
especially   if  one  is  trying  to,  say  determine  the  errors  in
separations.


Limitations

UVDIST                                                            Page 3


The program accepts input files containing (a) 20 or  fewer  stations,
(b) 10000 or fewer (non-deleted) u,v-points.

Program History

Version 1.0:  1983 Jun  5 - new program (TJP).
Version 2.0:  1984 Jan  3 - modified to accept MERGE-format  2  files,
          additional  XAXIS  options and parameters ERRORS, FLUX, FWHM
          (TJP/DLM/RLM).
Version 2.1:  1985 May 24 - Do not  die  if  station  coordinates  are
          missing (TJP).
Version 3.0:  1985 Jun  4 - Add XAXIS="UVPA" option (TJP).
Version 3.2:  1987 Mar  7 - Add XAXIS="PROJ" option (APM/TJP).