Basic Information on blflag

Task: blflag
Purpose: Interactive flagging task.
Categories: uv analysis

        BLFLAG is a Miriad task for flagging visibilities interactively.
        It plots visibilities (e.g. amplitude vs time), either one
        baseline at a time or all together, and allows discrepant points
        to be flagged with a cursor.
 
        Commands are entered as a single character at the keyboard:
          Left-Button  Left mouse button flags the nearest visibility.
          Right-Button Right mouse button causes BLFLAG to precede to
                       the next baseline.
          <CR>         Carriage-return gives help.
          ?            Help.
          a            Flag nearest visibility (same as left mouse
                       button).
          c            Clear the flagging for this baseline and redraw
                       plot.
          h            Give help (same as carriage return).
          p            Define a polygonal region, and flag visibilities
                       within this region.  Define the vertices of the
                       polygon by moving the cursor and then hitting the
                       left mouse button (or a).  Finish defining the
                       polygon by hitting the right mouse button (or x).
                       You can delete vertices with the middle mouse
                       button (or d).
          q            Abort completely.  This does not apply flagging.
          r            Redraw plot.
          u            Unzoom.
          x            Move to next baseline (same as right mouse
                       button).
          z            Zoom in.  You follow this by clicking the mouse
                       on the left and right limits to zoom.
 

Key: vis
        Input visibility dataset to be flagged.  No default.
 

Key: line
        The normal Miriad linetype specification.  BLFLAG averages all
        channels together before displaying them, flags being applied
        to all channels.  The default is all channels.
 

Key: device
        Normal PGPLOT plot device.  An interactive device, e.g. /xserve,
        must be selected.  No default.
 

Key: stokes
        Normal Stokes/polarisation parameter selection.  The default is
        'ii' (i.e. Stokes-I assuming the source is unpolarised).  NOTE
        BLFLAG plots the average of all the selected Stokes/polarisation
        quantities.  Also it flags ALL quantities, regardless of whether
        they were selected or not.
 

Key: select
        Normal visibility data selection.  Only selected data can be
        flagged.  The default is to select all data.
 

Key: axis
        Two character strings, giving the X and Y axes of the plot.
        Possible axis values are:
          time         (the default for the X axis)
          lst          Local apparent sidereal time.
          uvdistance   sqrt(u**2+v**2)
          hangle       (hour angle)
          channel      (implies nofqav)
          amplitude    (the default for the Y axis)
          phase
          real
          imaginary
          rms          Theoretical rms noise.
 

Key: xrange
        Plot range in the x-direction
          If axis = uvdistance            [kilo-lambda;   2 values]
          If axis = time                  [dd,hh,mm,ss.s; 8 values]
          If axis = amplitude, real, imag [natural units; 2 values]
          If axis = phase                 [degrees;       2 values]
          If axis = hangle                [hh,mm,ss.s;    6 values]
          If axis = rms                   [flux units;    2 values]
          If axis = lst                   [decimal hours; 2 values]
 
        For axis types other than 'time' or 'hangle', one or other of
        the limits may be set with the other self-scaled by specifying
        the lower limit as 'min' and the upper as 'max' (or simply
        omitting it).  For example,
 
          xrange=min,0
 
        self-scales the lower limit while pinning the upper limit to
        zero, whereas either of the following
 
          xrange=0,max
          xrange=0
 
        set the lower limit to zero while self-scaling the upper limit.
 
        Default is to self-scale both limits.
 

Key: yrange
        Plot range for the y-axis as for the x-axis.  The default is to
        self-scale.  For amplitude type plots you can greatly reduce the
        number of points to plot by using something like yrange=0.3 to
        cut out noise.
 

Key: options
        Task enrichment parameters.  Several can be given, separated by
        commas.  Minimum match is used.  Possible values are:
          nobase  Normally BLFLAG plots a single baseline at a time.
                  This option causes all baselines to be plotted on
                  a single plot.
          selgen  Generate a file appropriate for selecting the bad
                  data (via a select keyword).  The output is a text
                  file called "blflag.select".
          noapply Do not apply the flagging.
          rms     When processing spectra, blflag normally plots the
                  mean value of the spectra.  Using options=rms causes
                  it to plot the rms value instead.
          scalar  When processing spectra, blflag normally forms an
                  average value by vector averaging.  This option
                  causes it to generate the scalar average.  It should
                  be used with significant caution.
          nofqaver Do not average spectra - the resulting number of
                  points may be too large to handle.  Use select to
                  break up the data in time ranges or use yrange to
                  exclude noise.
        The following options can be used to disable calibration.
          nocal   Do not apply antenna gain calibration.
          nopass  Do not apply bandpass correction.
          nopol   Do not apply polarisation leakage correction.
 
Revision: 1.23, 2021/06/02 04:45:09 UTC