.. include:: references.txt
.. _nd-representations:
************************************
N-dimensional representation classes
************************************
For code blocks below and any pages linked below, we'll assume the following
imports have already been executed::
>>> import astropy.units as u
>>> import numpy as np
>>> import gala.dynamics as gd
Introduction
============
The Astropy |astropyrep|_ presently only support 3D positions and differential
objects. The `~gala.dynamics.NDCartesianRepresentation` and
`~gala.dynamics.NDCartesianDifferential` classes add Cartesian representation
classes that can handle arbitrary numbers of dimensions. For example, 2D
coordinates::
>>> xy = np.arange(16).reshape(2, 8) * u.kpc
>>> rep = gd.NDCartesianRepresentation(xy)
>>> rep
4D coordinates::
>>> x = np.arange(16).reshape(4, 4) * u.kpc
>>> rep = gd.NDCartesianRepresentation(x)
>>> rep
These can be passed in to the |psp| or |orb| classes as with any of the Astropy
core representation objects::
>>> xy = np.arange(16).reshape(2, 8) * u.kpc
>>> vxy = np.arange(16).reshape(2, 8) / 10. * u.kpc / u.Myr
>>> w = gd.PhaseSpacePosition(pos=xy, vel=vxy)
>>> fig = w.plot()
.. plot::
:align: center
import astropy.units as u
import numpy as np
import gala.dynamics as gd
xy = np.arange(16).reshape(2, 8) * u.kpc
vxy = np.arange(16).reshape(2, 8) / 10. * u.kpc / u.Myr
w = gd.PhaseSpacePosition(pos=xy, vel=vxy)
fig = w.plot()
However, certain functionality such as representation transformations, dynamical
quantity calculation, and coordinate frame transformations are disabled when the
number of dimensions is not 3 (i.e. when not using the Astropy core
representation classes).
N-dimensional representations API
---------------------------------
.. automodapi:: gala.dynamics.representation_nd
:no-heading:
:headings: ^^