NDCartesianDifferential¶

class
gala.dynamics.representation_nd.
NDCartesianDifferential
(d_x, unit=None, copy=True)[source]¶ Bases:
gala.dynamics.representation_nd.NDMixin
,astropy.coordinates.CartesianDifferential
Differentials in of points in ND cartesian coordinates.
 Parameters
 *d_x
Quantity
or array The Cartesian coordinates of the differentials. If not quantity,
unit
should be set. unit
Unit
or str If given, the differentials will be converted to this unit (or taken to be in this unit if not given.
 copybool, optional
If
True
(default), arrays will be copied rather than referenced.
 *d_x
Attributes Summary
Return an instance with the data transposed.
A tuple with the inorder names of the coordinate components.
Component ‘d_x’ of the Differential.
Return a vector array of the x, y, and z coordinates.
Component ‘d_y’ of the Differential.
Component ‘d_z’ of the Differential.
Container for meta information like name, description, format.
The number of dimensions of the instance and underlying arrays.
The shape of the instance and underlying arrays.
The size of the object, as calculated from its shape.
Methods Summary
copy
(*args, **kwargs)Return an instance containing copies of the internal data.
diagonal
(*args, **kwargs)Return an instance with the specified diagonals.
flatten
(*args, **kwargs)Return a copy with the array collapsed into one dimension.
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.
get_d_xyz
([xyz_axis])Return a vector array of the x, y, and z coordinates.
get_name
()Name of the representation or differential.
norm
([base])Vector norm.
ravel
(*args, **kwargs)Return an instance with the array collapsed into one dimension.
represent_as
(other_class, base)Convert coordinates to another representation.
reshape
(*args, **kwargs)Returns an instance containing the same data with a new shape.
squeeze
(*args, **kwargs)Return an instance with singledimensional shape entries removed
swapaxes
(*args, **kwargs)Return an instance with the given axes interchanged.
take
(indices[, axis, mode])Return a new instance formed from the elements at the given indices.
to_cartesian
([base])Convert the differential to 3D rectangular cartesian coordinates.
transpose
(*args, **kwargs)Return an instance with the data transposed.
Attributes Documentation

T
¶ Return an instance with the data transposed.
Parameters are as for
T
. All internal data are views of the data of the original.

attr_classes
= {}¶

components
¶ A tuple with the inorder names of the coordinate components.

d_x
¶ Component ‘d_x’ of the Differential.

d_xyz
¶ Return a vector array of the x, y, and z coordinates.
 Parameters
 xyz_axisint, optional
The axis in the final array along which the x, y, z components should be stored (default: 0).
 Returns
 d_xs
Quantity
With dimension 3 along
xyz_axis
.
 d_xs

d_y
¶ Component ‘d_y’ of the Differential.

d_z
¶ Component ‘d_z’ of the Differential.

info
¶ Container for meta information like name, description, format. This is required when the object is used as a mixin column within a table, but can be used as a general way to store meta information.

isscalar
¶

ndim
¶ The number of dimensions of the instance and underlying arrays.

shape
¶ The shape of the instance and underlying arrays.
Like
shape
, can be set to a new shape by assigning a tuple. Note that if different instances share some but not all underlying data, setting the shape of one instance can make the other instance unusable. Hence, it is strongly recommended to get new, reshaped instances with thereshape
method. Raises
 ValueError
If the new shape has the wrong total number of elements.
 AttributeError
If the shape of any of the components cannot be changed without the arrays being copied. For these cases, use the
reshape
method (which copies any arrays that cannot be reshaped inplace).

size
¶ The size of the object, as calculated from its shape.
Methods Documentation

copy
(*args, **kwargs)¶ Return an instance containing copies of the internal data.
Parameters are as for
copy()
.

diagonal
(*args, **kwargs)¶ Return an instance with the specified diagonals.
Parameters are as for
diagonal()
. All internal data are views of the data of the original.

flatten
(*args, **kwargs)¶ Return a copy with the array collapsed into one dimension.
Parameters are as for
flatten()
.

classmethod
from_cartesian
(other, base=None)¶ Convert the differential from 3D rectangular cartesian coordinates to the desired class.
 Parameters
 other :
The object to convert into this differential.
 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.
 Returns
 A new differential object that is this class’ type.

classmethod
from_representation
(representation, base)¶ 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

get_d_xyz
(xyz_axis=0)[source]¶ Return a vector array of the x, y, and z coordinates.
 Parameters
 xyz_axisint, optional
The axis in the final array along which the x, y, z components should be stored (default: 0).
 Returns
 d_xs
Quantity
With dimension 3 along
xyz_axis
.
 d_xs

classmethod
get_name
()¶ Name of the representation or differential.
In lower case, with any trailing ‘representation’ or ‘differential’ removed. (E.g., ‘spherical’ for
SphericalRepresentation
orSphericalDifferential
.)

norm
(base=None)¶ 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

ravel
(*args, **kwargs)¶ Return an instance with the array collapsed into one dimension.
Parameters are as for
ravel()
. Note that it is not always possible to unravel an array without copying the data. If you want an error to be raise if the data is copied, you should should assign shape(1,)
to the shape attribute.

represent_as
(other_class, base)¶ 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

reshape
(*args, **kwargs)¶ Returns an instance containing the same data with a new shape.
Parameters are as for
reshape()
. Note that it is not always possible to change the shape of an array without copying the data (seereshape()
documentation). If you want an error to be raise if the data is copied, you should assign the new shape to the shape attribute (note: this may not be implemented for all classes usingShapedLikeNDArray
).

squeeze
(*args, **kwargs)¶ Return an instance with singledimensional shape entries removed
Parameters are as for
squeeze()
. All internal data are views of the data of the original.

swapaxes
(*args, **kwargs)¶ Return an instance with the given axes interchanged.
Parameters are as for
swapaxes()
:axis1, axis2
. All internal data are views of the data of the original.

take
(indices, axis=None, mode='raise')¶ Return a new instance formed from the elements at the given indices.
Parameters are as for
take()
, except that, obviously, no output array can be given.

to_cartesian
(base=None)¶ 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
 This object as a
CartesianDifferential
 This object as a

transpose
(*args, **kwargs)¶ Return an instance with the data transposed.
Parameters are as for
transpose()
. All internal data are views of the data of the original.