%N select
This keyword selects the subset of the visibility data to be
processed. There are a number of subcommands, which may be
abbreviated. Each may be prefixed with a plus or minus sign to
indicate using or discarding the selected data. Many subcommands
can be given (separate them by commas). 
Examples:
'select=time(03OCT30:05:42:08,03OCT30:05:43:09),ant(7)(2)'
'select=-auto,-ant(7,8)'
'select=-ant(7,8),vis(1,15),vis(31,45),vis(301,1000)'
'select=-ant(7,8),-ant(1)(4,6),-ant(2)(4,5,6),-ant(3)(4,5),-ant(4)(5,6),-ant(5)(6)'

See also documentation for subroutine selprobe(), which may very well differ
slightly from this document.

Subcommands include:

  time(t1,t2)
Select data between times t1 and t2 (UT). Times are in the format:
  yymmmdd.fff
or
  yymmmdd:hh:mm:ss.s
Various abbreviations are possible. If no date part is given, then
the time matchs all data (regardless of its date) for the given
time of day. e.g. time(03OCT30:05:41:08,03OCT30:05:43:09)

  antennae(a1,a2,...)(b1,b2...)
Select all baselines pairs formed between first and second list of
antennas. The second list is optional and defaults to all antennas.

  uvrange(uvmin,uvmax)
Select visibilities with uv radius between uvmin and uvmax (in kilo
wavelenghts). If only one value is given, uvmin is taken as zero.

  uvnrange(uvmin,uvmax)
Select visibilities with uv radius between uvmin and uvmax (in
nanoseconds). If only one value is given, uvmin is taken as zero. 

  visibility(n1,n2)
Select visibilities numbered n1 to n2 inclusive.

  increment(inc)
Select every inc'th visibility.

  ra(r1,r2)
Select visibilities whose RA is in the range r1 to r2. RAs are given
in the format
  hh:mm:ss
or
  hh.hhh
Various abbreviations are possible.

  dec(d1,d2)
Select visibilites whose DEC is in the range d1 to d2. Declinations
are given in the format
  dd:mm:ss
or
  dd.ddd
Various abbreviations are possible.

  ha(h1,h2)
Selects on hour angle (values in decimal hours or hh:mm:ss)

  lst(lst1,lst2)
Selects on LST (values in decimal hours or hh:mm:ss)

  elevation(el1,el2)
Selects on elevation (values in degrees)

  dra(p1,p2)
Select visibilities for which the RA of the pointing center is offset
from the main pointing center by between p1 and p2 arcseconds.

  ddec(p1,p2)
Select visibilities for which the DEC of the pointing center is offset
from the main pointing center by between p1 and p2 arcseconds.

  dazim(p1,p2)
Select visibilities for which the DAZIM offset is between p1 and p2 arcseconds.

  delev(p1,p2)
Select visibilities for which the DELEV offset is between p1 and p2 arcseconds.

  pointing(p1,p2)
Select visibilities with the rms pointing error in the range p1 to p2
arcseconds. If only one number is given, p1 is taken as 0.

  polarization(p1,p2,p3,...)
Select visibilities on the basis of their polarization/Stokes parameter.
p1,p2,p3,... can be selected from "i,q,u,v,xx,yy,xy,yx,rr,ll,rl,lr"
Conversion between polarizations Stokes parameters (e.g. convert
linears to Stokes)  is not performed by this mechanism (see keyword stokes).

  source(SRCNAM1,SRCNAM2,...)
Select correlations from the particular source. Several sources
can be given. An asterisk in the source name is treated as a
wildcard. Note that the sourcename match is done IGNORING CASE. 

  purpose(TYPE)
Select based on the intent/purpose of the observation. Introduced in 
CARMA, where the letters B (bandpass), F (fluxcal), G (gaincal), 
P (polarization), R (radio pointing), S (science) and O (other) 
are used. 
Multiple letters from this set can be chooses. No wildcards allowed.

  seeing(r1,r2)
Select on seeing monitor rms path length (in microns). The UV variable used
is smonrms for ATCA, rmspath for CARMA

  frequency(f1,f2)
Select correlations, where the sky frequency of the first correlation
is in the range f1 to f2 (in GHz). If only a single frequency is
given, then correlations are selected if the first correlation
is within 1% of the given frequency.  Note this selects the whole
record.  This may include several spectral-windows whose frequency
is quite different from the first correlation in the first window.

  amplitude(amplo,amphi)
Select any correlation, where the amplitude is between "amplo" and
"amphi". If only one value is given, then "amphi" is assumed to be
infinite.

  shadow(d)
Selects data that would be shadowed by an antenna of diameter "d" meters. 
If "d" is zero, then the actual diameter of the antennas (if known) is used. 
If some data is shadowed, it is advisable to use an antenna diameter value 
greater than the physical antenna size (e.g. 20% larger).
See also the task CSFLAG for more finegrained approach for heterogeneous
arrays and dealing with sub arrays.

  bin(b1,b2)
Select visibilities which have pulsar bin numbers in the range
b1 to b2 inclusive. If b2 is omitted, just pulsar bin b1 is
selected.

  on(n)
This is used with single dish observations, anbd selects based
whether the "on" variable in the data is on (1) or off (0).

  auto
This is used with files that contain a mix of autocorrelations and
crosscorrelations. This selects just the autocorrelation data.

  window(w1,w2,...)
Select by spectral window (IF band in AIPS terminology). See
the help on window for more information.

  or
The list of subcommands before and after the 'or' are "ored"
together.

  and
Default ???
