numpy cheats #8
Description
convert an array of 2d vectors to 3d vectors.
see: https://stackoverflow.com/questions/36878089/python-add-a-column-to-numpy-2d-array
import numpy as np
array_2dvec = np.array([ [x1, y1], [x2, y2], [x3, y3] ])
array_3dvec = np.hstack( (array_2dvec, np.zeros((len(array_2dvec), 1)) ))