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ms.selecttaql - Function

1.3.1 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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