Syntax: ANGLE expr

   For most purposes, only the first element of the expr is used, let's
call it D, as it's an angle in degrees.

   ANGLE will cause text from LABEL to come out D degrees
anticlockwise from horizontal. It also causes points to be rotated
counter-clockwise by D. If D is non-zero it will be applied to axis
labels (note that 360 is non-zero).

   For plotting points the full vector of values is used, with each
point rotated by the corresponding element of expr. If more points are
specified than the dimension of expr, the first element will be used
for the excess.