[spec_out] = SplineRaw(wls_in, spec_in, wls_out, [extend])
Convert the wavelength representation of a spectrum.
Handling of out of range values:
extend == 0: Cubic spline, extends with zeros [default]
extend == 1: Cubic spline, extends with last value in that direction
extend == 2: Linear interpolation, linear extrapolation
spec_in may have multiple columns, in which case spec_out does as well.
wls_in and wls_out may be specified as a column vector of
wavelengths or as a [start delta num] description.
7/26/03 dhb Add extend argument
8/13/11 dhb Added linear extrapolation option for extend