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EXTREMA

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

    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  /PLOT  specifies  that instead of computing global extrema LOCAL
    extrema values should be computed, and 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.

    If  option /COMPUTE is not present, the extrema are only computed if not
    already known (from a previous call to EXTREMA, or from an  image  head-
    er).  /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 2011-04-01