Coordinate transformations methods

class pNbody._coordinate_transformations_mixin._NbodyCoordinateTransformationsMixin

Bases: object

sphericalvel2pos()

Replace Cartesian positions with spherical velocity components.

This method performs an in-place update of the pos attribute, mapping the calculated spherical velocity components ($v_r, v_{ heta}, v_{phi}$) directly to the Cartesian axes ($x, y, z$).

The mapping is assigned as follows: * pos[:, 0] (x-axis) $leftarrow$ $v_r$ (Radial velocity) * pos[:, 1] (y-axis) $leftarrow$ $v_{ heta}$ (Polar/Theta velocity) * pos[:, 2] (z-axis) $leftarrow$ $v_{phi}$ (Azimuthal/Phi velocity)

Notes

This operation is destructive to the original spatial position data. It is typically used to analyze the velocity-space structure in spherical coordinates.

vel2pos()

Replace particle positions with their current velocity vectors.

This method performs an in-place update of the pos attribute, mapping the Cartesian velocity components ($v_x, v_y, v_z$) directly to the Cartesian position coordinates ($x, y, z$).

This is commonly used in phase-space analysis or when visualizing velocity-space distributions.

Notes

This operation is destructive to the original position data unless it has been backed up elsewhere.

vel_cart2cyl(pos=None, vel=None)

Transform velocities from Cartesian to cylindrical coordinates.

Convert velocity components ($v_x, v_y, v_z$) into ($v_R, v_T, v_z$). The resulting $v_R$ represents radial motion in the xy-plane, and $v_T$ represents tangential (azimuthal) motion.

Parameters

  • pos (ndarray, optional) – A (N, 3) array of Cartesian positions [x, y, z]. If None, uses self.pos. Default is None.

  • vel (ndarray, optional) – A (N, 3) array of Cartesian velocities [vx, vy, vz]. If None, uses self.vel. Default is None.

Returns

A (N, 3) float32 array of cylindrical velocities [vR, vT, vz].

Return type

ndarray

vel_cyl2cart(pos=None, vel=None)

Transform velocities from cylindrical to Cartesian coordinates.

Convert velocity components ($v_R, v_T, v_z$) into ($v_x, v_y, v_z$). The transformation is position-dependent, as it relies on the local azimuthal orientation of each particle.

Parameters

  • pos (ndarray, optional) – A (N, 3) array of Cartesian positions [x, y, z]. If None, uses self.pos. Default is None.

  • vel (ndarray, optional) – A (N, 3) array of cylindrical velocities [vR, vT, vz]. If None, uses self.vel. Default is None.

Returns

A (N, 3) float32 array of Cartesian velocities [vx, vy, vz].

Return type

ndarray