NDCartesianDifferential

class gala.dynamics.representation_nd.NDCartesianDifferential(d_x, unit=None, copy=True)

Bases: NDMixin, CartesianDifferential

Differentials in of points in ND cartesian coordinates.

Parameters:

*d_xQuantity or array

The Cartesian coordinates of the differentials. If not quantity, unit should be set.

unitUnit 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.

Attributes Summary

T	Return an instance with the data transposed.
attr_classes
components	A tuple with the in-order 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.
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.
isscalar
mask	The combined mask of all components.
masked	Whether or not the instance uses masked values.
name	Name of the representation or differential.
ndim	The number of dimensions of the instance and underlying arrays.
shape	The shape of the instance and underlying arrays.
size	The size of the object, as calculated from its shape.
unmasked	Get an instance without the mask.

Methods Summary

copy(*args, **kwargs)	Return an instance containing copies of the internal data.
diagonal(*args, **kwargs)	Return an instance with the specified diagonals.
filled(fill_value)	Get a copy of the underlying data, with masked values filled in.
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_mask(*attrs)	Calculate the mask, by combining masks from the given attributes.
get_name()
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 single-dimensional shape entries removed.
swapaxes(*args, **kwargs)	Return an instance with the given axes interchanged.
take(indices[, axis, out, mode])	Return a new instance formed from the elements at the given indices.
to_cartesian([base])	Convert the differential to 3D rectangular cartesian coordinates.
transform(matrix[, base, transformed_base])	Transform differentials using a 3x3 matrix in a Cartesian basis.
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 in-order 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_xsQuantity

With dimension 3 along xyz_axis.

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

mask

The combined mask of all components.

masked

name: ClassVar[str] = 'ndcartesian'

Name of the representation or differential.

When a subclass is defined, by default, the name is the lower-cased name of the class with with any trailing ‘representation’ or ‘differential’ removed. (E.g., ‘spherical’ for SphericalRepresentation or SphericalDifferential.)

This can be customized when defining a subclass by setting the class attribute.

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 the reshape 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 in-place).

size

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

unmasked

Get an instance without the mask.

Note that while one gets a new instance, the underlying data will be shared.

See also

filled

get a copy of the underlying data, with masked values filled in.

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.

filled(fill_value)

Get a copy of the underlying data, with masked values filled in.

Parameters:

fill_valueobject

Value to replace masked values with.

Returns:

filledinstance

Copy of self with masked items replaced by fill_value.

See also

unmasked

get an instance without the mask.

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.

baseBaseRepresentation

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 instance

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:

representationBaseRepresentation 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.

get_d_xyz(xyz_axis=0)

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_xsQuantity

With dimension 3 along xyz_axis.

get_mask(*attrs)

Calculate the mask, by combining masks from the given attributes.

Parameters:

*attrsstr

Attributes from which to get the masks to combine. If not given, use all components of the class.

Returns:

maskndarray of bool

The combined, read-only mask. If the instance is not masked, it is an array of False with the correct shape.

classmethod get_name()

Deprecated since version v7.1: The get_name method is deprecated and may be removed in a future version. Use name instead.

Name of the representation or differential.

Returns the .name attribute.

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 non-angular 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.

Returns:

normastropy.units.Quantity

Vector norm, with the same shape as the representation.

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_classBaseRepresentation 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.

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 (see reshape() 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 using NDArrayShapeMethods).

squeeze(*args, **kwargs)

Return an instance with single-dimensional 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, out=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.

Returns:

CartesianDifferential

This object, converted.

transform(matrix, base=None, transformed_base=None)

Transform differentials 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.

base, transformed_baseCartesianRepresentation or None, optional

Not used in the Cartesian transformation.

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.