RadialRepresentation

class astropy.coordinates.RadialRepresentation(distance, differentials=None, copy=True)

Bases: BaseRepresentation

Representation of the distance of points from the origin.

Note that this is mostly intended as an internal helper representation. It can do little else but being used as a scale in multiplication.

Parameters:

distanceQuantity [:ref: ‘length’]

The distance of the point(s) from the origin.

differentialspython:dict, BaseDifferential, optional

Any differential classes that should be associated with this representation. The input must either be a single BaseDifferential instance (see _compatible_differentials for valid types), or a dictionary of of differential instances with keys set to a string representation of the SI unit with which the differential (derivative) is taken. For example, for a velocity differential on a positional representation, the key would be 's' for seconds, indicating that the derivative is a time derivative.

copybool, optional

If True (default), arrays will be copied. If False, arrays will be references, though possibly broadcast to ensure matching shapes.

Attributes Summary

attr_classes
distance	The distance from the origin to the point(s).

Methods Summary

from_cartesian(cart)	Converts 3D rectangular cartesian coordinates to radial coordinate.
norm()	Vector norm.
scale_factors()	Scale factors for each component's direction.
to_cartesian()	Cannot convert radial representation to cartesian.
transform(matrix)	Radial representations cannot be transformed by a Cartesian matrix.
unit_vectors()	Cartesian unit vectors are undefined for radial representation.

Attributes Documentation

attr_classes = {'distance': <class 'astropy.units.quantity.Quantity'>}

distance

The distance from the origin to the point(s).

Methods Documentation

classmethod from_cartesian(cart)

Converts 3D rectangular cartesian coordinates to radial coordinate.

norm()

Vector norm.

Just the distance itself.

Returns:

normQuantity [:ref: ‘dimensionless’]

Dimensionless ones, with the same shape as the representation.

scale_factors()

Scale factors for each component’s direction.

Given unit vectors \(\hat{e}_c\) and scale factors \(f_c\), a change in one component of \(\delta c\) corresponds to a change in representation of \(\delta c \times f_c \times \hat{e}_c\).

Returns:

scale_factorspython:dict of Quantity

The keys are the component names.

to_cartesian()

Cannot convert radial representation to cartesian.

transform(matrix)

Radial representations cannot be transformed by a Cartesian matrix.

Parameters:

matrixnumpy:array_like

The transformation matrix in a Cartesian basis. Must be a multiplication: a diagonal matrix with identical elements. Must have shape (…, 3, 3), where the last 2 indices are for the matrix on each other axis. Make sure that the matrix shape is compatible with the shape of this representation.

Raises:

ValueError

If the matrix is not a multiplication.

unit_vectors()

Cartesian unit vectors are undefined for radial representation.