; DFTPL
;---------------------------------------------------------------
;! plots DFT of a UV data set at arbitrary point versus time
;# Task Plot UV
;-----------------------------------------------------------------------
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;-----------------------------------------------------------------------
DFTPL     LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC
DFTPL     Plots the DFT of an arbitrary point using UV data
USERID       -32000.0    32000.0   File owner number - ignored
INNAME                             Input UV file name (name)
INCLASS                            Input UV file name (class)
INSEQ             0.0     9999.0   Input UV file name (seq. #)
INDISK            0.0        9.0   Input UV file disk unit #
UVRANGE           0.0              Range of projected spacings
                                     (thousands of wavelengths)
TIMERANG                           Time range to select:
                                     Start Day, Hour, Min, Sec
                                     End Day, Hour, Min, Sec
SHIFT                              Shift in asec at ref position
FREQID            0.0              Frequency ID number: 0 -> 1
BCHAN             0.0              First channel to include
ECHAN             0.0              Last channel to include
BIF               0.0              First IF to include
EIF               0.0              Last IF to include
BPARM                              Control parameters
                                   1 : Correlator number
                                   2 : averaging interval (sec)
                                   3 : > 0.0 => fixed scale
                                       < 0.0 => fixed range
                                   4 : Xmin (fixed scale)
                                   5 : Xmax (fixed scale)
                                   6 : Ymin (fixed scale)
                                   7 : Ymax (fixed scale)
                                   8 : X/Y axis ratio
                                   9 : 1 plots points only
                                       2 plots points and
                                         error bars
                                       3 plots histogram
                                      (If <=0 then print time,
                                       flux, and error also.)
                                   10 : scale factor for points
DOCIRCLE       -1.0         1.0    > 0 => extend ticks to form
                                   coordinate grid
LTYPE        -410.0       410.0    Type of labeling: 1 border,
                                   2 no ticks, 3 - 6 standard,
                                   7 - 10 only tick labels
                                   <0 -> no date/time
DOTV           -1.0         1.0    > 0 Do plot on the TV, else
                                   make a plot file
GRCHAN          0.0         8.0    Graphics channel 0 => 1.
----------------------------------------------------------------
DFTPL
Type: Task
Use:  Plots the DFT of the complex visibilities found in a UV data
      base for an arbitrary point in the sky as a function of time.
      Note that the visibilies are shifted under control of SHIFT and
      then the real parts are simply summed over all baselines in each
      time interval.  Task TBAVG makes a UV data set of the summed
      visibilities instead of plotting them.

      NOTE: This task does NOT apply any flag or calibration tables.
      Run SPLIT or other appropriate task before running DFTPL.
Adverbs:
  USERID.....Input file user number.  Ignored
  INNAME.....Input UV file name (name)    Standard defaults.
  INCLASS....Input UV file name (class)   Standard defaults.
  INSEQ......Input UV file name (seq. #)  0 => highest.
  INDISK.....Disk drive # of input UV file.  0 => any.
  CHANNEL....Spectral line channel number.   0 => 1.
  UVRANGE....Range (min, max) of projected baselines to include
             0,0 => all baselines
  TIMERANG...Time range of the data to be plotted. In order:
             Start day, hour, min, sec, End day, hour, min, sec.
             Days relative to reference date.  0 => full range.
  SHIFT......Shift in arcseconds - the data are shifted, summed, and
             then plotted.  These are shifts in arc seconds at the
             reference point -
             RA = RA0 + SHIFT(1)/cos(DEC0), DEC = DEC0 + SHIFT(2)
  FREQID.....To select one frequency ID number: 0 => 1.
  BCHAN......Average channels BCHAN-ECHAN; 0 -> 1
  ECHAN......Average channels BCHAN-ECHAN; 0 -> max
  BIF........Also average IFs BIF-EIF; 0 -> 1
  EIF........Also average IFs BIF-EIF; 0 -> max
  BPARM......Control parameters:
     1: 1 => plot RR data only    5 => plot Stokes I
        2 => plot LL data only    6 => plot Stokes V
        3 => plot RL data only    7 => plot Stokes Q
        4 => plot LR data only    8 => plot Stokes U
     2 = averaging interval in seconds (0 => 60)
         NOTE: an interval beginning at a sample time T1 will include
         all samples < T1+BPARM(2).  If your data occur at 5 second
         intervals and you want no averaging, set BPARM(2) < 5.  If
         you want to average pairs of samples, set 5 < BPARM(2) < 10.
     3 = if greater than zero, use BPARM(4) - BPARM(8) as the ranges
         of the axes.  If less than zero, use the BPARMs to limit the
         range of the axes, but self-scale the axes within that range.
         If 0.0, fully self-scaling.
     4 = Minimum of X-axis.  Units = days.
     5 = Maximum of X-axis (if = BPARM(4) do self-scale in X).
     6 = Minimum of Y-axis.  Units = Jy.
     7 = Maximum of Y-axis (if = BPARM(6) do self-scale in Y).
     8 = Ratio of X axis length to Y axis length.
     9 = If 1, simply plot up the point
           -1, plot points and print out results (0 => -1)
         If 2, plot points and error bars
           -2, plot points, error bars, and print out results
         If 3, plot points in histogram form
           -3, plot histogram and print out results
  DOCIRCLE...False (<= 0) means that tick marks are short lines
             extending inward from the plot borders.  True (>0)
             requests that a full coordinate grid be drawn.
  LTYPE.......Labelling type, see HELP LTYPE for details:
              1 = border, 2 = no ticks, 3 or 7 = standard, 4 or 8 =
              relative to ref. pixel, 5 or 9 = relative to subimage
              (BLC, TRC) center, 6 or 10 = pixels.  7-10 all labels
              other than tick numbers and axis type are omitted.
              Less than 0 is the same except that the plot file
              version number and create time are omitted.
              Add n * 100 to alter the metric scaling.
  DOTV.......> 0 => plot directly on the TV device, otherwise make a
             plot file for later display on one or more devices
             (including the TV if desired).
  GRCHAN.....Graphics channel (1 - 7) to use for line drawing. 0 => 1.
----------------------------------------------------------------
DFTPL:  Plots DFT using data from a u,v data base.
PROGRAMMER: T.Bastian, Univ. of Colorado
RELATED PROGRAMS: TKPL,PRTPL,TVPL

                            COMMENTS

     DFTPL was written primarily to assist stellar observers
interested in time variable phenomena (e.g., outbursts on RS CVn's,
dMe flare stars, etc.). Since these stars are in general unresolved,
it's often pointless to make a synthesis map for each time interval.
Instead one can do the following: 1) make a large field map using the
entire XY sorted data base and identify all background sources; 2) run
APCLN or MX with boxes around these sources (but not the stellar
source of interest) and CLEAN them down to the noise; 3) using the
resulting CLEAN components as a model of the background sources, use
UVSUB to subtract the model from the UV data base; 4) use UVSRT to
sort the data into TB order.
      If NO confusing sources of any importance can be found in the
field, then of course steps 1-4 can be skipped and one simply begins
with a TB sorted (calibated and edited) data base. he UV data base on
an EXPORT tape is sorted in TB order, but one might have to use the
verb PUTHEAD to indicate this fact in the header.  This is done by
first setting KEYWORD to 'SORT' and KEYSTRING to 'TB' and typing PUTH.
      The task DFTPL allows one to plot the direct fourier transform
of the measured visibilities as a function of time for an arbitrary
shift in RA and DEC.  It will plot either points, points with error
bars, or histogram format. The averaging interval is adjustable
(BPARM(2)).  The data time segment may be specified (through APARM).
The task runs somewhat faster than UVPLT.  Hence one can moniter all
Stoke's parameters of a star with time VERY quickly, without having to
resort to generating a tedious sucession of maps.
