cartesian2compass

  CARTESIAN2COMPASS - Convert angles from cartiesian to compass

   C = CARTESIAN2COMPASS(R, USERADIANS)

   Converts angles from cartesian format to compass.
   In compass, 0 degrees is up, and angles rotate clockwise.
   In cartesian, 0 degrees is rightward, and angles rotate
   counterclockwise.

   If USERADIANS is 1, radians are used; otherwise, 
   degrees are used.