def test_represent_as():
from astropy.coordinates.builtin_frames import ICRS
icrs = ICRS(ra=1 * u.deg, dec=1 * u.deg)
cart1 = icrs.represent_as('cartesian')
cart2 = icrs.represent_as(r.CartesianRepresentation)
cart1.x == cart2.x
cart1.y == cart2.y
cart1.z == cart2.z
# now try with velocities
icrs = ICRS(ra=0 * u.deg,
dec=0 * u.deg,
distance=10 * u.kpc,
pm_ra_cosdec=0 * u.mas / u.yr,
pm_dec=0 * u.mas / u.yr,
radial_velocity=1 * u.km / u.s)
# single string
rep2 = icrs.represent_as('cylindrical')
assert isinstance(rep2, r.CylindricalRepresentation)
assert isinstance(rep2.differentials['s'], r.CylindricalDifferential)
# single class with positional in_frame_units, verify that warning raised
with catch_warnings() as w:
icrs.represent_as(r.CylindricalRepresentation, False)
assert len(w) == 1
assert w[0].category == AstropyWarning
assert 'argument position' in str(w[0].message)
# TODO: this should probably fail in the future once we figure out a better
# workaround for dealing with UnitSphericalRepresentation's with
# RadialDifferential's
# two classes
# rep2 = icrs.represent_as(r.CartesianRepresentation,
# r.SphericalCosLatDifferential)
# assert isinstance(rep2, r.CartesianRepresentation)
# assert isinstance(rep2.differentials['s'], r.SphericalCosLatDifferential)
with pytest.raises(ValueError):
icrs.represent_as('odaigahara')
def test_represent_as():
from astropy.coordinates.builtin_frames import ICRS
icrs = ICRS(ra=1*u.deg, dec=1*u.deg)
cart1 = icrs.represent_as('cartesian')
cart2 = icrs.represent_as(r.CartesianRepresentation)
cart1.x == cart2.x
cart1.y == cart2.y
cart1.z == cart2.z
# now try with velocities
icrs = ICRS(ra=0*u.deg, dec=0*u.deg, distance=10*u.kpc,
pm_ra_cosdec=0*u.mas/u.yr, pm_dec=0*u.mas/u.yr,
radial_velocity=1*u.km/u.s)
# single string
rep2 = icrs.represent_as('cylindrical')
assert isinstance(rep2, r.CylindricalRepresentation)
assert isinstance(rep2.differentials['s'], r.CylindricalDifferential)
# single class with positional in_frame_units, verify that warning raised
with catch_warnings() as w:
icrs.represent_as(r.CylindricalRepresentation, False)
assert len(w) == 1
assert w[0].category == AstropyWarning
assert 'argument position' in str(w[0].message)
# TODO: this should probably fail in the future once we figure out a better
# workaround for dealing with UnitSphericalRepresentation's with
# RadialDifferential's
# two classes
# rep2 = icrs.represent_as(r.CartesianRepresentation,
# r.SphericalCosLatDifferential)
# assert isinstance(rep2, r.CartesianRepresentation)
# assert isinstance(rep2.differentials['s'], r.SphericalCosLatDifferential)
with pytest.raises(ValueError):
icrs.represent_as('odaigahara')
def test_frame_api():
from astropy.coordinates.representation import SphericalRepresentation, \
UnitSphericalRepresentation
from astropy.coordinates.builtin_frames import ICRS, FK5
# <--------------------Reference Frame/"Low-level" classes--------------------->
# The low-level classes have a dual role: they act as specifiers of coordinate
# frames and they *may* also contain data as one of the representation objects,
# in which case they are the actual coordinate objects themselves.
# They can always accept a representation as a first argument
icrs = ICRS(UnitSphericalRepresentation(lon=8 * u.hour, lat=5 * u.deg))
# which is stored as the `data` attribute
assert icrs.data.lat == 5 * u.deg
assert icrs.data.lon == 8 * u.hourangle
# Frames that require additional information like equinoxs or obstimes get them
# as keyword parameters to the frame constructor. Where sensible, defaults are
# used. E.g., FK5 is almost always J2000 equinox
fk5 = FK5(UnitSphericalRepresentation(lon=8 * u.hour, lat=5 * u.deg))
J2000 = time.Time('J2000')
fk5_2000 = FK5(UnitSphericalRepresentation(lon=8 * u.hour, lat=5 * u.deg),
equinox=J2000)
assert fk5.equinox == fk5_2000.equinox
# the information required to specify the frame is immutable
J2001 = time.Time('J2001')
with pytest.raises(AttributeError):
fk5.equinox = J2001
# Similar for the representation data.
with pytest.raises(AttributeError):
fk5.data = UnitSphericalRepresentation(lon=8 * u.hour, lat=5 * u.deg)
# There is also a class-level attribute that lists the attributes needed to
# identify the frame. These include attributes like `equinox` shown above.
assert all(nm in ('equinox', 'obstime')
for nm in fk5.get_frame_attr_names())
# the result of `get_frame_attr_names` is called for particularly in the
# high-level class (discussed below) to allow round-tripping between various
# frames. It is also part of the public API for other similar developer /
# advanced users' use.
# The actual position information is accessed via the representation objects
assert_allclose(icrs.represent_as(SphericalRepresentation).lat, 5 * u.deg)
# shorthand for the above
assert_allclose(icrs.spherical.lat, 5 * u.deg)
assert icrs.cartesian.z.value > 0
# Many frames have a "default" representation, the one in which they are
# conventionally described, often with a special name for some of the
# coordinates. E.g., most equatorial coordinate systems are spherical with RA and
# Dec. This works simply as a shorthand for the longer form above
assert_allclose(icrs.dec, 5 * u.deg)
assert_allclose(fk5.ra, 8 * u.hourangle)
assert icrs.representation_type == SphericalRepresentation
# low-level classes can also be initialized with names valid for that representation
# and frame:
icrs_2 = ICRS(ra=8 * u.hour, dec=5 * u.deg, distance=1 * u.kpc)
assert_allclose(icrs.ra, icrs_2.ra)
# and these are taken as the default if keywords are not given:
# icrs_nokwarg = ICRS(8*u.hour, 5*u.deg, distance=1*u.kpc)
# assert icrs_nokwarg.ra == icrs_2.ra and icrs_nokwarg.dec == icrs_2.dec
# they also are capable of computing on-sky or 3d separations from each other,
# which will be a direct port of the existing methods:
coo1 = ICRS(ra=0 * u.hour, dec=0 * u.deg)
coo2 = ICRS(ra=0 * u.hour, dec=1 * u.deg)
# `separation` is the on-sky separation
assert coo1.separation(coo2).degree == 1.0
# while `separation_3d` includes the 3D distance information
coo3 = ICRS(ra=0 * u.hour, dec=0 * u.deg, distance=1 * u.kpc)
coo4 = ICRS(ra=0 * u.hour, dec=0 * u.deg, distance=2 * u.kpc)
assert coo3.separation_3d(coo4).kpc == 1.0
# The next example fails because `coo1` and `coo2` don't have distances
with pytest.raises(ValueError):
assert coo1.separation_3d(coo2).kpc == 1.0
def test_frame_api():
from astropy.coordinates.representation import SphericalRepresentation, \
UnitSphericalRepresentation
from astropy.coordinates.builtin_frames import ICRS, FK5
# <--------------------Reference Frame/"Low-level" classes--------------------->
# The low-level classes have a dual role: they act as specifiers of coordinate
# frames and they *may* also contain data as one of the representation objects,
# in which case they are the actual coordinate objects themselves.
# They can always accept a representation as a first argument
icrs = ICRS(UnitSphericalRepresentation(lon=8*u.hour, lat=5*u.deg))
# which is stored as the `data` attribute
assert icrs.data.lat == 5*u.deg
assert icrs.data.lon == 8*u.hourangle
# Frames that require additional information like equinoxs or obstimes get them
# as keyword parameters to the frame constructor. Where sensible, defaults are
# used. E.g., FK5 is almost always J2000 equinox
fk5 = FK5(UnitSphericalRepresentation(lon=8*u.hour, lat=5*u.deg))
J2000 = time.Time('J2000')
fk5_2000 = FK5(UnitSphericalRepresentation(lon=8*u.hour, lat=5*u.deg), equinox=J2000)
assert fk5.equinox == fk5_2000.equinox
# the information required to specify the frame is immutable
J2001 = time.Time('J2001')
with raises(AttributeError):
fk5.equinox = J2001
# Similar for the representation data.
with raises(AttributeError):
fk5.data = UnitSphericalRepresentation(lon=8*u.hour, lat=5*u.deg)
# There is also a class-level attribute that lists the attributes needed to
# identify the frame. These include attributes like `equinox` shown above.
assert all(nm in ('equinox', 'obstime') for nm in fk5.get_frame_attr_names())
# the result of `get_frame_attr_names` is called for particularly in the
# high-level class (discussed below) to allow round-tripping between various
# frames. It is also part of the public API for other similar developer /
# advanced users' use.
# The actual position information is accessed via the representation objects
assert_allclose(icrs.represent_as(SphericalRepresentation).lat, 5*u.deg)
# shorthand for the above
assert_allclose(icrs.spherical.lat, 5*u.deg)
assert icrs.cartesian.z.value > 0
# Many frames have a "default" representation, the one in which they are
# conventionally described, often with a special name for some of the
# coordinates. E.g., most equatorial coordinate systems are spherical with RA and
# Dec. This works simply as a shorthand for the longer form above
assert_allclose(icrs.dec, 5*u.deg)
assert_allclose(fk5.ra, 8*u.hourangle)
assert icrs.representation_type == SphericalRepresentation
# low-level classes can also be initialized with names valid for that representation
# and frame:
icrs_2 = ICRS(ra=8*u.hour, dec=5*u.deg, distance=1*u.kpc)
assert_allclose(icrs.ra, icrs_2.ra)
# and these are taken as the default if keywords are not given:
# icrs_nokwarg = ICRS(8*u.hour, 5*u.deg, distance=1*u.kpc)
# assert icrs_nokwarg.ra == icrs_2.ra and icrs_nokwarg.dec == icrs_2.dec
# they also are capable of computing on-sky or 3d separations from each other,
# which will be a direct port of the existing methods:
coo1 = ICRS(ra=0*u.hour, dec=0*u.deg)
coo2 = ICRS(ra=0*u.hour, dec=1*u.deg)
# `separation` is the on-sky separation
assert coo1.separation(coo2).degree == 1.0
# while `separation_3d` includes the 3D distance information
coo3 = ICRS(ra=0*u.hour, dec=0*u.deg, distance=1*u.kpc)
coo4 = ICRS(ra=0*u.hour, dec=0*u.deg, distance=2*u.kpc)
assert coo3.separation_3d(coo4).kpc == 1.0
# The next example fails because `coo1` and `coo2` don't have distances
with raises(ValueError):
assert coo1.separation_3d(coo2).kpc == 1.0
