Python ICRS.represent_as方法代码示例

# 需要导入模块: from astropy.coordinates.builtin_frames import ICRS [as 别名]
# 或者: from astropy.coordinates.builtin_frames.ICRS import represent_as [as 别名]
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')

# 需要导入模块: from astropy.coordinates.builtin_frames import ICRS [as 别名]
# 或者: from astropy.coordinates.builtin_frames.ICRS import represent_as [as 别名]
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