Basic Information on lagflg

Task: lagflg
Purpose: Flag visibility data in the lag domain.
Categories: calibration

LAGFLG is a Miriad task to flag visibility data in the lag domain.
As visibility flags are correlation-based (not lag based), this task
has to produce a new outpput file.

Ideally, the input visibility file would be before Hanning smoothing
(if any), any calibration has been applied, and certainly before any
subsetting of the visibility spectrum has been performed.

This requires that the number of channels is 2**n+1, for some value of
n.

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

Key: out
Output visibility file, after flagging. No default.

Key: lags
A list of pairs, giving the lags to be flagged. Each pair gives
a range of lag values. These are indices, with the zero lag having
the value 0. This is the same lag numbering system used by uvspec
when displaying lags. No default - at least one range pair must be
given.

Key: select
Normal visibility selection. See the help on select for more
information. All data in the input is copied to the output, but
only those data selected using the select keyword will go through
the lag flagging process. Currently only "polarization", "antenna"
and "time" selection is supported in this task. This should be
sufficient to select a correlator product that is bad over a
particular period.

Key: options
This gives extra processing options. Several options can be given,
each separated by commas. They may be abbreviated to the minimum 
needed to avoid ambiguity. Possible options are:
  noflag    By default, "lagflg" zeros flagged data before it
            transforms to the lag domain. At times this might
            no be desirable - in which case use this option.

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