e = Frames.axis(axis);
A unit vector e is returned depending on whether x-, y-, or z-axis is required.
 axis  |    e
-------+-----------
  1    |  {1,0,0}
  2    |  {1,0,0}
  3    |  {1,0,0}
function axis extends Modelica.Icons.Function; input Integer axis(min = 1, max = 3) "Axis vector to be returned"; output Real e[3](each final unit = "1") "Unit axis vector"; end axis;