Documentation on uvflag

Task: uvflag
Purpose: Flags or unflags uv data
Categories: calibration, uv analysis

        UVFLAG is used to change flags corresponding to visibility data.
        Using the keywords select, line and edge one selects a portion of a
        uv-data file. For all selected correlations the flags are then set to
        the value specified with the keyword flagval. If flagval equals
        'flag', the uv data are flagged as bad; for flagval equal to 'unflag',
        the uv data are flagged as good.
        The user can control the amount of output produced using the options
        keyword. Only records that fulfill all selection criteria as
        specified by select, line and edge are shown and counted, not the
        complete datafile.
        Because the physical writing of the flags is done using a buffering
        approach, the flags are only actually changed in the datafile if
        one lets uvflag finish normally. I.e., if the 'q' option is used to
        stop printing, the flags may or may not have been changed.
        UVFLAG can also be used to inspect the uv-data. If option 'noapply'
        is used, everything works as it would do normally, except that the
        flags are not actually changed in the datafile. This is particularly
        useful in combination with option 'full'.

Key: vis
	Standard vis keyword. See the help on vis for more information.
        Multiple input datasets are allowed.

Key: select
	Standard select keyword. See the help on select for more information.

Key: line
	Standard line keyword. See the help on line for more information.
        Uvflag supports only types 'channel and wide'. If line is
        unspecified, both the 'channel data' and the 'wideband data'
        (if present) will be flagged. Also, since averaging of data
        is an undefined operation when setting flags, width is
        forced to be equal to 1.

Key: edge
        This keyword allows uvflag to work on the edges of spectral
        windows. Three numbers may be given, n, m and c. Flags will
        be changed only for the first n and last m channels of each
        spectral window and for the central c channels.
        If one value is given, the number of selected channels at
        the start and end of the window is assumed to be equal.
        If two values are given the first gives the number of
        selected channels at the start, the second the number at
        the end. In this case either one may also be 0.
        The third value gives the number of channels to delete from
        the center of the band. The default is 0. Any negative
        number is interpreted as meaning that the middle 1/8th of
        the band around the center must be deleted. The center of a
        window is defined as 'startchannel+nchannels/2'.
        Use of the edge keyword forces the step parameter of the
        line keyword to be equal to 1.
        Edge cannot be combined with linetype 'wide'. If edge is
        used, the linetype defaults to channel,0,1,1,1, i.e. all
        channels.
        This also works for multiple input visibility files, even
        if these have different correlator modes.
        [0,0,0]

Key: flagval
        Either 'flag' or 'unflag', which tells whether the flags for
        the correlations selected by 'select', 'line' and 'edge'
        have to be set or unset. May be abbreviated to 'f' or 'u'.
        Exactly one of the options 'flag' or 'unflag' must be
        present.

Key: options
        One or more of
          'noapply',
          'none', 'brief', 'indicative', 'full', 'noquery',
          'hms', 'decimal'.

        These options can be abbreviated to uniqueness. The default
        is 'brief,hms', except when a logfile is given (see keyword
        log), then it becomes 'indicative,hms'.

        'noapply' will go through the whole process without
        actually changing the flags. Useful for checking what will
        happen or for inspecting the flags.
        No history comments are written.

        'none', 'brief', 'indicative' and 'full' control the
        amount of information returned to the user. 
          - 'brief' gives an overview when UVFLAG finishes.
          - 'indicative' lists the number of good, bad and changed
             flags for each selected uv-record.
          - 'full' lists the data, the old flag and the new flag for
             each channel separately and also an overview of each record.
          - If more than 1 verbosity level is given, the lowest is taken.
          - Option 'noquery' will turn off the feature that printing
            is halted every 22 lines.

        For verbosity levels 'indicative' and 'full' the format
        of the time that is written is determined by 'hms' (hours,
        minutes and seconds) or 'decimal' (decimal parts of a day).

Key: log
        Name of a file where reported information is written.
        If empty this implies the terminal screen, else the
        named file. Giving a filename also sets option 'indicative'.
        [terminal]