1.2.1.0 ms.selecttaql

ms.selecttaql - Function

1.2.1 Select a subset of the measurement set.
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 False and send a warning message in the logger. Otherwise this function will return True. To undo all the selections you need to use the selectinit function (with reset=True). Note that index values used in the TaQL string are zero-based as are all tool indices.

Arguments


Inputs
msselect	TaQL selection string
	allowed:	string
	Default:

Returns
bool

Example

      ms.open("3C273XC1.MS")
      ms.selectinit(datadescid=0)
      ms.select({’antenna1’:[0,2,4],’uvdist’:[1200.,1900.]})
      ms.selecttaql(’ANTENNA1==2’)
      ms.range(["ANTENNA1","ANTENNA2"])
      # {’antenna1’: array([2]),
      #  ’antenna2’: array([ 6,  9, 11, 18, 20, 21, 24])}

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 zero, two or four 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, zero-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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