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        [GREG2\]EXTREMA [/BLANKING Bval  Eval]  [/PLOT]  [/COMPUTE]  [/LOCAL

    Computes  and  shows  the minimum and maximum values of the Regular Grid
    array: shows XMIN,XMAX,YMIN,YMAX,ZMIN,ZMAX. A useful command for  decid-
    ing  where to set contour levels, or what size to give to the BOX if you
    want an exact aspect ratio between two coordinates. The current blanking
    value is used, but can be overridden using option /BLANKING.

    Option  /LOCAL  specifies that instead of computing global extrema LOCAL
    extrema values should be computed and:
      - PLOT: written at appropriate places on the plot. This is a very good
        way  to  avoid ambiguities in contour map. A shortest format is used
        for writing the values, and the character size  controls  the  label
        size. /PLOT is an alias for /LOCAL PLOT.
      - TERMINAL: written to the terminal,
      - FileName: written to the given file name.
    These  arguments  can  be combined. If output is TERMINAL and/or file, X
    and Y values are offsets in radians.

    If option /COMPUTE is not present, the global extrema are only  computed
    if  not already known (from a previous call to EXTREMA, or from an image
    header). /COMPUTE forces computation from the data array. It  should  be
    used  if  for  any reason the known extrema are incorrect (invalid image
    header, killed bad pixel, change of blanking value...).

Gildas manager 2020-12-01