next up previous contents index
Next: FILE Up: LAS Language Internal Help Previous: DUMP   Contents   Index


        LAS\EXTRACT [X1 X2 [Unit]] [/INDEX]

    In  its  default mode, EXTRACT copies R into T, extracts a subsection of
    R, and save the result in R. If the option /INDEX is present, or if  SET
    ACTION  is  INDEX,  a subsection of each observation in the index is ex-
    tracted and saved in the output file.

    Without arguments, the cursor is invoked (if available)  to  define  the
    subsection range. If the arguments X1 and X2 are present, the subsection
    is defined by this range, in the given Unit (if any) or  by  default  in
    the  current  X axis unit (SET UNIT). X2 can be indifferently greater or
    lower than X1, and Unit is a single  character  in  the  four  C)hannel,
    V)elocity, F)requency or I)mage. Note that if Unit is F or I, the number
    of extracted channels can vary for two similar observations (same setup)
    because of different Doppler factors.

    If the range overlaps the input spectrum limits, a warning is raised and
    the missing data is filled with the blanking value. Requesting  a  range
    off the input spectrum is an error. The command FIND /FREQUENCY can help
    you to build an index with spectra  overlapping  one  frequency  or  one
    range of frequencies.

    On return, the observation header is consistently updated: the reference
    channel is shifted and number of  channels  updated.  The  PLOT  section
    (which  remembers  the  previous plotting limits) is disabled because it
    probably does not makes sense for the extracted data array.

    Only regularly sampled X axes are supported.

Gildas manager 2019-08-20