Plane Selection (chans, stokes)

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6.1.2 Plane Selection (chans, stokes)

The channel, frequency, or velocity plane(s) of the image is chosen using the chans parameter:

chans      =      ’’   #  Select the channel(spectral) range

#          string containing channel range

#          immath, imstat, and imcontsub - takes a string listing
#          of channel numbers, velocity, and/or frequency
#          numbers, much like the spw paramter
#          Only channel numbers acceptable at this time.
#          Default: none (all);
#          Example: chans=’3~20’
#                   chans="0,3,4,8"
#                   chans="3~20,50,51"

The polarization plane(s) of the image is chosen with the stokes parameter:

stokes     =      ’’   #  Stokes params to image (I,IV,IQU,IQUV)

#          string containing Stokes selections

#          Stokes parameters to image, may or may not be separated
#          by commas but best if you use commas.
#          Default: none (all); Example: stokes=’IQUV’;
#          Example:stokes=’I,Q’
#          Options: ’I’,’Q’,’U’,’V’,
#                   ’RR’,’RL’,’LR’,’LL’,
#                   ’XX’,’YX’,’XY’,’YY’,...

To get help on these parameters, see the in-line help

help(par.chans)
help(par.stokes)

Sometimes, as in the immoments task, the channel/plane selection is generalized to work on more than one axis type. In this case, the planes parameter is used. This behaves like chans in syntax.

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