CartesianRepresentation

class astropy.coordinates.CartesianRepresentation(x, y=None, z=None, unit=None, xyz_axis=None, copy=True)

Bases: astropy.coordinates.BaseRepresentation

Representation of points in 3D cartesian coordinates.

Parameters:

x, y, z : Quantity or array

The x, y, and z coordinates of the point(s). If x, y, and z have different shapes, they should be broadcastable. If not quantity, unit should be set. If only x is given, it is assumed that it contains an array with the 3 coordinates are stored along xyz_axis.

unit : Unit or str

If given, the coordinates will be converted to this unit (or taken to be in this unit if not given.

xyz_axis : int, optional

The axis along which the coordinates are stored when a single array is provided rather than distinct x, y, and z (default: 0).

copy : bool, optional

If True (default), arrays will be copied rather than referenced.

Attributes Summary

attr_classes
x	The x component of the point(s).
xyz	Return a vector array of the x, y, and z coordinates.
y	The y component of the point(s).
z	The z component of the point(s).

Methods Summary

cross(other)	Cross product of two representations.
dot(other)	Dot product of two representations.
from_cartesian(other)
get_xyz([xyz_axis])	Return a vector array of the x, y, and z coordinates.
mean(\*args, \*\*kwargs)	Vector mean.
sum(\*args, \*\*kwargs)	Vector sum.
to_cartesian()
transform(matrix)	Transform the cartesian coordinates using a 3x3 matrix.

Attributes Documentation

attr_classes = OrderedDict([(u'x', <class 'astropy.units.quantity.Quantity'>), (u'y', <class 'astropy.units.quantity.Quantity'>), (u'z', <class 'astropy.units.quantity.Quantity'>)])

x

The x component of the point(s).

xyz

Return a vector array of the x, y, and z coordinates.

Parameters:

xyz_axis : int, optional

The axis in the final array along which the x, y, z components should be stored (default: 0).

Returns:

xyz : Quantity

With dimension 3 along xyz_axis.

y

The y component of the point(s).

z

The z component of the point(s).

Methods Documentation

cross(other)

Cross product of two representations.

Parameters:

other : representation

If not already cartesian, it is converted.

Returns:

cross_product : CartesianRepresentation

With vectors perpendicular to both self and other.

dot(other)

Dot product of two representations.

Parameters:

other : representation

If not already cartesian, it is converted.

Returns:

dot_product : Quantity

The sum of the product of the x, y, and z components of self and other.

classmethod from_cartesian(other)

get_xyz(xyz_axis=0)

Return a vector array of the x, y, and z coordinates.

Parameters:

xyz_axis : int, optional

The axis in the final array along which the x, y, z components should be stored (default: 0).

Returns:

xyz : Quantity

With dimension 3 along xyz_axis.

mean(*args, **kwargs)

Vector mean.

Returns a new CartesianRepresentation instance with the means of the x, y, and z components.

Refer to mean for full documentation of the arguments, noting that axis is the entry in the shape of the representation, and that the out argument cannot be used.

sum(*args, **kwargs)

Vector sum.

Returns a new CartesianRepresentation instance with the sums of the x, y, and z components.

Refer to sum for full documentation of the arguments, noting that axis is the entry in the shape of the representation, and that the out argument cannot be used.

to_cartesian()

transform(matrix)

Transform the cartesian coordinates using a 3x3 matrix.

This returns a new representation and does not modify the original one.

Parameters:

matrix : ndarray

A 3x3 transformation matrix, such as a rotation matrix.

Examples

We can start off by creating a cartesian representation object:

>>> from astropy import units as u
>>> from astropy.coordinates import CartesianRepresentation
>>> rep = CartesianRepresentation([1, 2] * u.pc,
...                               [2, 3] * u.pc,
...                               [3, 4] * u.pc)

We now create a rotation matrix around the z axis:

>>> from astropy.coordinates.matrix_utilities import rotation_matrix
>>> rotation = rotation_matrix(30 * u.deg, axis='z')

Finally, we can apply this transformation:

>>> rep_new = rep.transform(rotation)
>>> rep_new.xyz  
<Quantity [[ 1.8660254 , 3.23205081],
           [ 1.23205081, 1.59807621],
           [ 3.        , 4.        ]] pc>