BASE

        LAS\BASE [Deg] [/PLOT [Ipen]] [/INDEX] [/OBS] [/CONTINUUM [flux]]
        LAS\BASE SINUS Amplitude Period Phase [/PLOT [Ipen]]
        LAS\BASE LAST [/PLOT [Ipen]]

    When working on single spectra, BASE copies R  into  T,  then  subtracts
    from  R a polynomial baseline of degree Deg, or a sinusoidal baseline if
    the first argument is SINUS. Zones defined by the SET WINDOW command are
    not  used to fit the baseline. The T content may be recovered with SWAP.

    BASE SINUS Amplitude Period Phase
    (Phase is in the same unit as the period, usually km/s or MHz)  Subtract
    a  sinusoid.  Minimization will be done including also a linear baseline
    in addition to the sinusoid.

    BASE LAST
    Use the last determined baseline instead of computing a new one. It  can
    be  useful  to find a baseline from one backend and apply it to another.
    This also applies for sinusoidal baselines. 0th and 1st order  polynomi-
    als, and sinus fit are extrapolated if the R spectrum extends beyond the
    LAST spectrum limits. 2nd order (and higher) polynomials are not extrap-
    olated and the edge values are used beyond the LAST spectrum limits.

    BASE /PLOT
    Plot this baseline after the minimization, using the Ipen-th pen proper-
    ties. The pencil 2 (red at startup) is used by default.

    BASE /INDEX
    Subtracts a baseline to all records that have been loaded.  This  option
    is  not  needed if SET ACTION INDEX. /PLOT and /INDEX options are incom-
    patibles.

    BASE /OBS
    indicate that the baseline is to be fitted to the current R  buffer  ob-
    servations.  This  option  is not needed if the action level is OBS (de-
    fault). /OBS and /INDEX are incompatible.

    BASE /CONTINUUM
    Divide the spectrum by the baseline rather than subtracting it and  mul-
    tiply  by  the average flux. This is useful to keep the continuum level,
    when continuum is present and variations  of  atmospheric  emission  are
    properly subtracted out by fast enough switching.  This is of course the
    case for correlation spectra (e.g. coming from an  interferometer).  The
    continuum level will be adjusted to the value of the argument 'flux', if
    present; e.g. /CONTINUUM 1.0 will produce a spectrum of line-to-continu-
    um ratio. BASE /CONTINUUM does not work with BASE LAST or BASE SINUS.