Rebin to Reference Scale :

This routine is similar to REBIN AND DEFINE SCALE except that the x-values of the reference AAR (see MAKE REFERENCE) is used instead of the user defined x-scale.  Here we explain the various options and then give a detailed description of the algorithm.  We will refer to (wavelength, flux) and (x, y) interchangeably.
epsilon is used to eliminate multiple x-values as discussed below.