BaseDifferential¶

class
astropy.coordinates.
BaseDifferential
(*args, **kwargs)[source]¶ Bases:
astropy.coordinates.BaseRepresentationOrDifferential
A base class representing differentials of representations.
These represent differences or derivatives along each component. E.g., for physics spherical coordinates, these would be \(\delta r, \delta \theta, \delta \phi\).
 Parameters
 d_comp1, d_comp2, d_comp3
Quantity
or subclass The components of the 3D differentials. The names are the keys and the subclasses the values of the
attr_classes
attribute. copybool, optional
If
True
(default), arrays will be copied. IfFalse
, arrays will be references, though possibly broadcast to ensure matching shapes.
 d_comp1, d_comp2, d_comp3
Notes
All differential representation classes should subclass this base class, and define an
base_representation
attribute with the class of the regularBaseRepresentation
for which differential coordinates are provided. This will set up a defaultattr_classes
instance with names equal to the base component names prefixed byd_
, and all classes set toQuantity
, plus properties to access those, and a default__init__
for initialization.Methods Summary
from_cartesian
(other, base)Convert the differential from 3D rectangular cartesian coordinates to the desired class.
from_representation
(representation, base)Create a new instance of this representation from another one.
norm
([base])Vector norm.
represent_as
(other_class, base)Convert coordinates to another representation.
to_cartesian
(base)Convert the differential to 3D rectangular cartesian coordinates.
transform
(matrix, base, transformed_base)Transform differential using a 3x3 matrix in a Cartesian basis.
Methods Documentation

classmethod
from_cartesian
(other, base)[source]¶ Convert the differential from 3D rectangular cartesian coordinates to the desired class.
 Parameters
 other
The object to convert into this differential.
 base
BaseRepresentation
The points for which the differentials are to be converted: each of the components is multiplied by its unit vectors and scale factors. Will be converted to
cls.base_representation
if needed.
 Returns
BaseDifferential
subclass instanceA new differential object that is this class’ type.

classmethod
from_representation
(representation, base)[source]¶ Create a new instance of this representation from another one.
 Parameters
 representation
BaseRepresentation
instance The presentation that should be converted to this class.
 baseinstance of
cls.base_representation
The base relative to which the differentials will be defined. If the representation is a differential itself, the base will be converted to its
base_representation
to help convert it.
 representation

norm
(base=None)[source]¶ Vector norm.
The norm is the standard Frobenius norm, i.e., the square root of the sum of the squares of all components with nonangular units.
 Parameters
 baseinstance of
self.base_representation
Base relative to which the differentials are defined. This is required to calculate the physical size of the differential for all but Cartesian differentials or radial differentials.
 baseinstance of
 Returns
 norm
astropy.units.Quantity
Vector norm, with the same shape as the representation.
 norm

represent_as
(other_class, base)[source]¶ Convert coordinates to another representation.
If the instance is of the requested class, it is returned unmodified. By default, conversion is done via cartesian coordinates.
 Parameters
 other_class
BaseRepresentation
subclass The type of representation to turn the coordinates into.
 baseinstance of
self.base_representation
Base relative to which the differentials are defined. If the other class is a differential representation, the base will be converted to its
base_representation
.
 other_class

to_cartesian
(base)[source]¶ Convert the differential to 3D rectangular cartesian coordinates.
 Parameters
 baseinstance of
self.base_representation
The points for which the differentials are to be converted: each of the components is multiplied by its unit vectors and scale factors.
 baseinstance of
 Returns
CartesianDifferential
This object, converted.

transform
(matrix, base, transformed_base)[source]¶ Transform differential using a 3x3 matrix in a Cartesian basis.
This returns a new differential and does not modify the original one.
 Parameters
 matrix(3,3) array_like
A 3x3 (or stack thereof) matrix, such as a rotation matrix.
 baseinstance of
cls.base_representation
Base relative to which the differentials are defined. If the other class is a differential representation, the base will be converted to its
base_representation
. transformed_baseinstance of
cls.base_representation
Base relative to which the transformed differentials are defined. If the other class is a differential representation, the base will be converted to its
base_representation
.