1.3.1.0 ms.split - Function

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ms.split - Function

1.3.1 make a new ms from a subset of an existing ms, adjusting subtables and indices

Description

This function splits out part of the MS into a new MS. Time and channel averaging can be performed in the process (but not in the same call).

When splitting multiple spectral windows, the parameters nchan, start, step can be vectors, so that each spectral window has its own selection on averaging and number of output channels. But the option of using only one value for each of these parameters means that it will be replicated for all the spectral windows selected.

Arguments


Inputs
outputms	The name of the resulting measurement set
	allowed:	string
	Default:
field	Fields to include, by names or 0-based ids. (” => all)
	allowed:	variant
	Default:
spw	Spectral windows (and :channels) to select
	allowed:	variant
	Default:	*
step	number of input per output channels - Int vector of length 1 or same as spw
	allowed:	intArray
	Default:	1
baseline	Antenna names or indices to select (” => all)
	allowed:	variant
	Default:
timebin	Duration for averaging. Defaults to no averaging.
	allowed:	variant
	Default:	-1s
time	Only use data in the given time range, using the msselection syntax.
	allowed:	string
	Default:
scan	Only use the scan numbers requested using the msselection syntax.
	allowed:	variant
	Default:
uvrange	Limit data by uv distance using the msselection syntax.
	allowed:	variant
	Default:
taql	For the TAQL experts, flexible data selection using the TAQL syntax
	allowed:	string
	Default:
whichcol	’DATA’, ’MODEL_DATA’, ’CORRECTED_DATA’, ’FLOAT_DATA’, ’LAG_DATA’, and/or ’all’
	allowed:	string
	Default:	DATA
tileshape	Tile shape of the disk data columns, most users should not need to touch this parameter [0] => normal tiling, [1] => fast mosaic style tile [4,15,351] => a tile shape of 4 pol 15 chan and 351 rows
	allowed:	variant
	Default:
subarray	Limit data to specific (sub)array numbers.
	allowed:	variant
	Default:
combine	Ignore changes in these columns (scan, and/or state) when time averaging.
	allowed:	string
	Default:
correlation	Limit data to specific correlations (LL, XX, LR, XY, etc.).
	allowed:	string
	Default:
intent	Only use the requested scan intents.
	allowed:	string
	Default:
obs	Only use the requested observation IDs.
	allowed:	string
	Default:

Returns
bool

Example

  ms.open("multiwin.ms")
  ms.split(’subms.ms’, field=[0], spw=[0], nchan=[10],
           start=[0], step=[5], whichcol=’CORRECTED_DATA’)

  In this example we split out data from the 1st field and 1st
  spectral window. The output data will have 10 channels which is
  taken from 50 channels from the input data starting at channel 0 and
  averaging every 5.

  ms.open("multiwin.ms")
  ms.split(’subms.ms’, field=[0], spw=[0,1,2,3], nchan=[10],
           start=[0], step=[5], whichcol=’CORRECTED_DATA’)

In this example we split out data from the 1st field and four spectral
windows. The output data will have 4 spectral windows each of 10
channels which is taken from 50 channels from the input data starting
at channel 0 and averaging every 5.

  ms.open("multiwin.ms")
  ms.split(’subms.ms’, field=[0], spw=[0,1,2,3], nchan=[10,10,30,40],
           start=[0,4,9,9], step=[1,10,5,2], whichcol=’CORRECTED_DATA’)

In this example we split out data from the 1st field and four spectral
windows. There will be four spectral windows in the output data,
with 10, 10, 30 and 40 channels respectively. These are averages
of the input spectral windows. The first output spectral window
will be formed by picking 10 channels, starting at 0 with no
averaging, of the input spwid 0. The second output spectral window
will consists of 10 channels and is formed by picking 100 channels
from spwid 1 of the input data, starting at channel 4, and every
10 channels to make one output channel.

  ms.open("WSRT.ms")
  ms.split(’subms.ms’, timebin=’20s’, whichcol=’all’, combine=’scan’)
  ms.close()

  This example averages a WSRT MS into 20s bins, selecting whichever of DATA,
  MODEL_DATA, CORRECTED_DATA, or FLOAT_DATA, or LAG_DATA is present.  Normally
  the bins would not cross scans, but in this MS the scan number goes up with
  each integration, making it redundant enough with time that it would defeat
  any time averaging.  Therefore the combine parameter forces the SCAN column
  to be ignored for setting the bins.

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