# RadialRepresentation¶

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

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: distance : Quantity The distance of the point(s) from the origin. differentials : 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. copy : bool, optional If True (default), arrays will be copied rather than referenced.

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(self) Vector norm. scale_factors(self) Scale factors for each component’s direction. to_cartesian(self) Cannot convert radial representation to cartesian. unit_vectors(self) 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)[source]

Converts 3D rectangular cartesian coordinates to radial coordinate.

norm(self)[source]

Vector norm.

Just the distance itself.

Returns: norm : Quantity Dimensionless ones, with the same shape as the representation.
scale_factors(self)[source]

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_factors : dict of Quantity The keys are the component names.
to_cartesian(self)[source]

Cannot convert radial representation to cartesian.

unit_vectors(self)[source]

Cartesian unit vectors are undefined for radial representation.