def convertlineartostokes(vis):
"""Convert linear polarisations (XX, XY, YX, YY) into Stokes parameters.
Args:
vis (obj): ARL visibility data.
Returns:
vis: Converted visibility data.
"""
vis.data['vis'] = convert_linear_to_stokes(vis.data['vis'], polaxis=1)
vis.polarisation_frame = PolarisationFrame('stokesIQUV')
return vis
def convert_polimage_to_stokes(im: Image):
"""Convert a polarisation image to stokes (complex)
"""
assert isinstance(im, Image)
assert im.data.dtype == 'complex'
if im.polarisation_frame == PolarisationFrame('linear'):
cimarr = convert_linear_to_stokes(im.data)
return create_image_from_array(cimarr, im.wcs, PolarisationFrame('stokesIQUV'))
elif im.polarisation_frame == PolarisationFrame('circular'):
cimarr = convert_circular_to_stokes(im.data)
return create_image_from_array(cimarr, im.wcs, PolarisationFrame('stokesIQUV'))
else:
raise ValueError("Cannot convert %s to stokes" % (im.polarisation_frame.type))
def convert_visibility_to_stokes(vis):
"""Convert the polarisation frame data into Stokes parameters.
Args:
vis (obj): ARL visibility data.
Returns:
vis: Converted visibility data.
"""
poldef = vis.polarisation_frame
if poldef == PolarisationFrame('linear'):
vis.data['vis'] = convert_linear_to_stokes(vis.data['vis'], polaxis=1)
vis.polarisation_frame = PolarisationFrame('stokesIQUV')
elif poldef == PolarisationFrame('circular'):
vis.data['vis'] = convert_circular_to_stokes(vis.data['vis'],
polaxis=1)
vis.polarisation_frame = PolarisationFrame('stokesIQUV')
return vis
def test_stokes_linear_stokes_conversion(self):
stokes = numpy.array([1, 0.5, 0.2, -0.1])
linear = convert_stokes_to_linear(stokes)
assert_array_almost_equal(
convert_linear_to_stokes(linear).real, stokes, 15)
