BASE

 

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

    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. In
    the latter case, SINUS must be followed by  the  Amplitude,  Period  and
    Phase  (in  the same unit as the period, usually km/s or MHz) of a trial
    sinusoid. Minimization will be done including also a linear baseline  in
    addition  to  the  sinusoid. Zones defined by the SET WINDOW command are
    not used to fit the baseline.
             BASE LAST will 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.
             /PLOT  plots this baseline after the minimization.

    BASE /CONTINUUM will divide the spectrum by  the  baseline  rather  than
    substracting  it.  This  is  useful  to  keep  the continuum level, when
    continuum is present and variations of atmospheric emission are properly
    substracted  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-
    continuum  ratio.  BASE  /CONTINUUM does not work with BASE LAST or BASE
    SINUS.

    For On-The-Fly scans, BASE subtracts a basline  on  all  the  individual
    spectra.