def skymodel_cal_fit_skymodel(vis, calskymodel, gain=0.1, method='fit', **kwargs):
"""Fit a single skymodel to a visibility
This is the update to the component part of the window.
:param evis: Expected vis for this ssm
:param calskymodel: scm element being fit i.e. (skymodel, gaintable) tuple
:param gain: Gain in step
:param method: 'fit' or 'sum'
:param kwargs:
:return: skycomponent
"""
cvis = convert_blockvisibility_to_visibility(vis)
new_comps = list()
for comp in calskymodel[0].components:
new_comp = copy_skycomponent(comp)
if method == 'sum':
new_flux, _ = sum_visibility(cvis, new_comp.direction)
new_comp.flux = gain * new_flux + (1.0 - gain) * comp[0].flux
else:
new_comp, _ = fit_visibility(cvis, new_comp)
new_comp.flux = gain * new_comp.flux + (1.0 - gain) * comp.flux
new_comps.append(new_comp)
return SkyModel(components=new_comps)
def _checkcomponents(self,
dirty,
fluxthreshold=1.0,
positionthreshold=1.0,
check_dft=False):
comps = find_skycomponents(dirty,
fwhm=1.0,
threshold=10 * fluxthreshold,
npixels=5)
assert len(comps) == len(self.components), "Different number of components found: original %d, recovered %d" % \
(len(self.components), len(comps))
cellsize = abs(dirty.wcs.wcs.cdelt[0])
for comp in comps:
# Check for agreement in direction
ocomp = find_nearest_component(comp.direction, self.components)
radiff = abs(comp.direction.ra.deg -
ocomp.direction.ra.deg) / cellsize
assert radiff < positionthreshold, "Component differs in dec %.3f pixels" % radiff
decdiff = abs(comp.direction.dec.deg -
ocomp.direction.dec.deg) / cellsize
assert decdiff < positionthreshold, "Component differs in dec %.3f pixels" % decdiff
# Check for agreement between in flux image and DFT
if check_dft:
for comp in comps:
sflux = sum_visibility(self.componentvis, comp.direction)[0]
assert abs(comp.flux[0, 0] - sflux[0, 0]) < fluxthreshold, \
"Fitted and DFT flux differ %s %s" % (comp.flux[0, 0], sflux[0, 0])
def test_visibilitysum(self):
self.vis = create_visibility(self.lowcore, self.times, self.frequency,
channel_bandwidth=self.channel_bandwidth, phasecentre=self.phasecentre, weight=1.0,
polarisation_frame=PolarisationFrame("stokesIQUV"))
self.vismodel = predict_skycomponent_visibility(self.vis, self.comp)
# Sum the visibilities in the correct_visibility direction. This is limited by numerical precision
summedflux, weight = sum_visibility(self.vismodel, self.compreldirection)
assert_allclose(self.flux, summedflux, rtol=1e-7)
def test_sum_visibility(self):
self.vis = create_visibility(self.lowcore, self.times, self.frequency,
channel_bandwidth=self.channel_bandwidth,
phasecentre=self.phasecentre,
polarisation_frame=PolarisationFrame("linear"),
weight=1.0)
self.vis = predict_skycomponent_visibility(self.vis, self.comp)
flux, weight = sum_visibility(self.vis, self.comp.direction)
assert numpy.max(numpy.abs(flux - self.flux)) < 1e-7
def sagecal_fit_component(evis, theta, gain=0.1, method='fit', **kwargs):
"""Fit a single component to a visibility i.e. A13
This is the update to the component part of the window
:param evis:
:param theta:
:param kwargs:
:return:
"""
cvis = convert_blockvisibility_to_visibility(evis)
new_comp = copy_skycomponent(theta[0])
if method == 'sum':
new_flux, _ = sum_visibility(cvis, new_comp.direction)
new_comp.flux = gain * new_flux + (1.0 - gain) * theta[0].flux
else:
new_comp, _ = fit_visibility(cvis, new_comp)
new_comp.flux = gain * new_comp.flux + (1.0 - gain) * theta[0].flux
return new_comp