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##

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. Polynomial baseline degree must be in range
0-100. Areas 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 [Flux]
1) Divide the spectrum by the baseline (rather than subtracting it), and
then 2) multiply by the average flux. This is useful to keep the contin-
uum level, when continuum is present and variations of atmospheric emis-
sion are properly subtracted out by fast enough switching. This is of
course the case for correlation spectra (e.g. coming from an interferom-
eter). 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.

Gildas manager
2020-10-13