ms.selecttaql - Function

Select a subset of the measurement set.

Synopsis
selecttaql(msselect)

Arguments

msselect	in	TaQL selection string
		Allowed:	String
		Default:	no default

Returns
Boolean

Description
This function will select a subset of the current measurement set based on the standard TaQL selection string given.

Repeated use of this function, with different arguments, will further refine the selection, resulting in a successively smaller selected measurement set. If the selected measurement set does not contain any rows then this function will return F and send a warning message in the logger. Otherwise this function will return T. To undo all the selections you need to use the selectinit function (with reset=T). Note that index values used in the TaQL string are zero-based, whereas the other commands in this tool use one-based indices.

Example

      include 'ms.g'
      myms := ms("3C273XC1.ms");
      myms.selectinit(datadescid=1)
      myms.select([antenna1=[1,3,5],uvdist=[1200,1900]]);
      myms.selecttaql('ANTENNA1==2');
      myms.range("ANTENNA1 ANTENNA2")
      [antenna1=3, antenna2=[7 10 12 19 21 22 25] ]

This example selects all the data from the measurement set where the value in the DATA_DESC_ID column is zero. This corresponds to a particular spectral window and polarization setup. It then selects all the data where the first antenna in the interferometer is number one, three or five and where the uv distance is between 1200 and 1900 meters. Finally it uses a query to select all the data for which the ANTENNA1 column is 2 (this selects the middle antenna of the previous, one-based, selection). The selections are cumulative so that at the end of this example only data in the specified time range, with the specified, interferometers, uv distances, spectral window and polarization setup are selected.

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	Package	general
	Module	ms
	Tool	ms