def as_msindex(self):
"""
Return a dictionary of selected indices.
"""
with casa.OpenMS(self.vis) as ms:
status = ms.msselect(self.as_msselection(), onlyparse=True)
idx = ms.msselectedindices()
return idx
def readvis(self,
items=visconverter.VisibilityConverter.required_columns,
columns=[],
interval=0.0,
nrow=0,
adddefault=True):
"""
read visibility data accoding to the data selection
provided to constructor.
columns -- iteration axis
interval -- time interval to group together
nrow -- number of row for returned data chunk
adddefault -- add default sort columns to iteration axis
"""
vis = self.visparam.vis
msselect = self.visparam.as_msselection()
datacolumn = self.visparam.datacolumn.lower()
items = items.copy()
index = items.index('data')
if datacolumn == 'corrected':
items[index] = 'corrected_data'
elif datacolumn == 'residual':
items[index] = 'residual_data'
with casa.OpenMS(vis) as ms:
ms.msselect(msselect, onlyparse=False)
# method names depend on CASA version
ms_iterinit = getattr(ms, self.iterinit)
ms_iterorigin = getattr(ms, self.iterorigin)
ms_getdata = getattr(ms, self.getdata)
ms_iternext = getattr(ms, self.iternext)
# not using new iterator as it doesn't support
# reading meta information such as UVW...
# iterate through MS using VI/VB2 framework
ms_iterinit(columns, interval, nrow, adddefault)
more_chunks = ms_iterorigin()
chunk_id = 0
while (more_chunks):
rec = ms_getdata(items)
rec['chunk_id'] = chunk_id
yield rec
more_chunks = ms_iternext()
chunk_id += 1
if chunk_id % 100 == 0:
print('\rread {0} visibility chunks'.format(chunk_id),
end='',
file=sys.stderr)
print('\rread {0} visibility chunks'.format(chunk_id),
file=sys.stderr)
print('DONE reading visibility chunks')
def suggest_imaging_param(visparam):
vis = visparam.vis
msselect = visparam.as_msselection()
with casa.OpenMS(vis) as ms:
ms.msselect(msselect, onlyparse=False)
data = ms.getdata(['uvw', 'data_desc_id', 'antenna1', 'antenna2'])
uvw = data['uvw']
ddid = data['data_desc_id']
antenna1 = data['antenna1']
antenna2 = data['antenna2']
observing_frequency = ImageConfigurationHelper.get_observing_frequency(
vis)
antenna_diameter = ImageConfigurationHelper.get_antenna_diameter(vis)
# maximum antenna primary beam size [arcsec]
min_freq = min(observing_frequency.values()) * 1e-9 # Hz -> GHz
min_diameter = min(antenna_diameter)
primary_beam = ImageConfigurationHelper.calc_primary_beam(
min_diameter, min_freq)
qa = casa.CreateCasaQuantity()
c = qa.convert(qa.constants('c'), 'm/s')['value']
nrow = len(ddid)
umax = 0.0
vmax = 0.0
for irow in range(nrow):
f = observing_frequency[ddid[irow]]
u = uvw[0, irow] / c * f
v = uvw[1, irow] / c * f
umax = max(umax, u)
vmax = max(vmax, v)
rad2arcsec = 180.0 / numpy.pi * 3600.0
dl = 1.0 / (2 * umax) * rad2arcsec # rad -> arcsec
dm = 1.0 / (2 * vmax) * rad2arcsec # rad -> arcsec
M = int(numpy.ceil(primary_beam / dl)) + 12
N = int(numpy.ceil(primary_beam / dm)) + 12
suggested = {
'cell': ['{}arcsec'.format(dl), '{}arcsec'.format(dm)],
'imsize': [M, N]
}
return suggested