def _check_coord_repr_diff_types(c):
if isinstance(c.data, r.UnitSphericalRepresentation):
raise ConvertError("Transforming to/from a Galactocentric frame "
"requires a 3D coordinate, e.g. (angle, angle, "
"distance) or (x, y, z).")
if ('s' in c.data.differentials and isinstance(
c.data.differentials['s'],
(r.UnitSphericalDifferential, r.UnitSphericalCosLatDifferential,
r.RadialDifferential))):
raise ConvertError("Transforming to/from a Galactocentric frame "
"requires a 3D velocity, e.g., proper motion "
"components and radial velocity.")
def transform_to(self, frame, merge_attributes=True):
# a modified version of the corresponding astropy function.
from astropy.coordinates.errors import ConvertError
frame_kwargs = {}
# Frame name (string) or frame class? Coerce into an instance.
try:
frame = _get_frame_class(frame)()
except Exception:
pass
if isinstance(frame, SkyCoord):
frame = frame.frame # Change to underlying coord frame instance
if isinstance(frame, BaseCoordinateFrame):
new_frame_cls = frame.__class__
# Get frame attributes, allowing defaults to be overridden by
# explicitly set attributes of the source if ``merge_attributes``.
for attr in frame_transform_graph.frame_attributes:
self_val = getattr(self, attr, None)
frame_val = getattr(frame, attr, None)
if (frame_val is not None
and not (merge_attributes
and frame.is_frame_attr_default(attr))):
frame_kwargs[attr] = frame_val
elif (self_val is not None
and not self.is_frame_attr_default(attr)):
frame_kwargs[attr] = self_val
elif frame_val is not None:
frame_kwargs[attr] = frame_val
else:
raise ValueError('Transform `frame` must be a frame name, class, or instance')
# Hacky solution here -- Frames other than LunarTopo cannot accept a MoonLocation object
# and can get confused by it. Do not pass along `location` unless certain it will work.
moonloc_incompatible = not isinstance(frame, LunarTopo)
graph_attrs = frame_transform_graph.frame_attributes
if hasattr(self, 'location'):
loc = getattr(self, 'location')
if isinstance(loc, MoonLocation):
if moonloc_incompatible:
frame_kwargs.pop('location')
elif 'location' in graph_attrs.keys() \
and isinstance(graph_attrs['location'], MoonLocationAttribute):
frame_transform_graph.frame_attributes['location'] = \
EarthLocationAttribute(default=None)
# Get the composite transform to the new frame
trans = frame_transform_graph.get_transform(self.frame.__class__, new_frame_cls)
if trans is None:
raise ConvertError('Cannot transform from {} to {}'
.format(self.frame.__class__, new_frame_cls))
# Make a generic frame which will accept all the frame kwargs that
# are provided and allow for transforming through intermediate frames
# which may require one or more of those kwargs.
generic_frame = GenericFrame(frame_kwargs)
# Do the transformation, returning a coordinate frame of the desired
# final type (not generic).
new_coord = trans(self.frame, generic_frame)
# Finally make the new SkyCoord object from the `new_coord` and
# remaining frame_kwargs that are not frame_attributes in `new_coord`.
for attr in (set(new_coord.get_frame_attr_names())
& set(frame_kwargs.keys())):
frame_kwargs.pop(attr)
return self.__class__(new_coord, **frame_kwargs)
def transform_to(self, frame):
"""
Transform this coordinate to a new frame.
Parameters
----------
frame : str or `BaseCoordinateFrame` class / instance or `SkyCoord` instance
The frame to transform this coordinate into.
Returns
-------
coord : `SkyCoord`
A new object with this coordinate represented in the `frame` frame.
Raises
------
ValueError
If there is no possible transformation route.
"""
from astropy.coordinates.errors import ConvertError
if frame is None or isinstance(self.frame, NoFrame):
raise ValueError('Cannot transform to/from this SkyCoord because '
'the frame was not specified at creation.')
frame_kwargs = {}
# Frame name (string) or frame class? Coerce into an instance.
try:
frame = _get_frame_class(frame)()
except:
pass
if isinstance(frame, SkyCoord):
frame = frame.frame # Change to underlying coord frame instance
if isinstance(frame, BaseCoordinateFrame):
new_frame_cls = frame.__class__
# Set the keyword args for making a new frame instance for the
# transform. If the supplied frame instance has a non-default
# value set then use that, otherwise use the self attribute value
# if it is not None.
for attr in FRAME_ATTR_NAMES_SET():
self_val = getattr(self, attr, None)
frame_val = getattr(frame, attr, None)
if (frame_val is not None and
attr not in frame._attr_names_with_defaults):
frame_kwargs[attr] = frame_val
elif self_val is not None:
frame_kwargs[attr] = self_val
else:
raise ValueError('Transform `frame` must be a frame name, class, or instance')
# Get the composite transform to the new frame
trans = frame_transform_graph.get_transform(self.frame.__class__, new_frame_cls)
if trans is None:
raise ConvertError('Cannot transform from {0} to {1}'
.format(self.frame.__class__, new_frame_cls))
# Make a generic frame which will accept all the frame kwargs that
# are provided and allow for transforming through intermediate frames
# which may require one or more of those kwargs.
generic_frame = GenericFrame(frame_kwargs)
# Do the transformation, returning a coordinate frame of the desired
# final type (not generic).
new_coord = trans(self.frame, generic_frame)
# Finally make the new SkyCoord object from the `new_coord` and
# remaining frame_kwargs that are not frame_attributes in `new_coord`.
# We could remove overlaps here, but the init code is set up to accept
# overlaps as long as the values are identical (which they must be).
return self.__class__(new_coord, **frame_kwargs)