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

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

differentialsdict, 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. Vector norm. Scale factors for each component’s direction. Cannot convert radial representation to cartesian. transform(matrix) Radial representations cannot be transformed by a Cartesian matrix. 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()[source]

Vector norm.

Just the distance itself.

Returns
norm

Dimensionless ones, with the same shape as the representation.

scale_factors()[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

The keys are the component names.

to_cartesian()[source]

Cannot convert radial representation to cartesian.

transform(matrix)[source]

Radial representations cannot be transformed by a Cartesian matrix.

Parameters
matrixarray_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()[source]

Cartesian unit vectors are undefined for radial representation.