create_visibility_from_ms

create_visibility_from_ms(msname, channum=None, start_chan=None, end_chan=None, ack=False, datacolumn='DATA', selected_sources=None, selected_dds=None, average_channels=False)[source]

Minimal MS to Visibility converter

The MS format is much more general than the RASCIL Visibility so we cut many corners. This requires casacore to be installed. If not an exception ModuleNotFoundError is raised.

Creates a list of Visibility’s, split by field and spectral window

Reading of a subset of channels is possible using either start_chan and end_chan or channnum. Using start_chan and end_chan is preferred since it only reads the channels required. Channum is more flexible and can be used to read a random list of channels.

Parameters

  • msname – File name of MS

  • channum – range of channels e.g. range(17,32), default is None meaning all

  • start_chan – Starting channel to read

  • end_chan – End channel to read

  • ack – Ask casacore to acknowledge each table operation

  • datacolumn – MS data column to read DATA, CORRECTED_DATA, or MODEL_DATA

  • selected_sources – Sources to select

  • selected_dds – Data descriptors to select

  • average_channels – Average all channels read

Returns

List of Visibility

For example:

selected_sources = ['1302+5748', '1252+5634']
bvis_list = create_visibility_from_ms('../../data/3C277.1_avg.ms', datacolumn='CORRECTED_DATA',
                                   selected_sources=selected_sources)
sources = numpy.unique([bv.source for bv in bvis_list])
print(sources)
['1252+5634' '1302+5748']