coords.Coords.spiral

Coords.spiral(dir=(0, 1, 2), scale=(1.0, 1.0, 1.0), rfunc=<function Coords.<lambda>>, zfunc=<function Coords.<lambda>>, angle_spec=0.017453292519943295)

Perform a spiral transformation.

This is similar to cylindrical_to_cartesian() but allows the specification of two functions defining extra transformation functions for the r and z directions to produce spiral and helical geometries.

Parameters

dir, scale, angle_spec: see cylindrical_to_cartesian()

rfunc: callable, optional

Function r(theta) taking one float parameter and returning a float. The values rfunc(theta) are added to the provided r. The theta values are according to angle_spec.

zfunc: callable, optional

Function z(theta) taking one float parameter and returning a float. The values rfunc(theta) are added to the provided z. The theta values are according to angle_spec.

Notes

The default rfunc converts points along the y-axis into an Archimedes spiral.

Examples

Create an Archimedes spiral with two turns and a point every 10 degrees

>>> X = Coords([[0.0,   0.0, 0.0],
...             [0.0,  90.0, 0.0],
...             [0.0, 180.0, 0.0],
...             [0.0, 270.0, 0.0],
...             [0.0, 360.0, 0.0],
...             [0.0, 450.0, 0.0],
...             [0.0, 540.0, 0.0],
...             [0.0, 630.0, 0.0],
...             [0.0, 720.0, 0.0]])
>>> Y = X.spiral()
>>> print(Y[::4]) # print one point every turn
[[0. 0. 0.]
 [1. 0. 0.]
 [2. 0. 0.]]