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        [GREG2\]RANDOM_MAP [Arg1 [Arg2]] [/NEIGHBOURS Nb] [/TRIANGLES] [/EX-

    This  command  is  a  general purpose interpolation task which uses data
    from the X, Y and Z arrays (or those specified in option /VARIABLES)  to
    fill  in  a Regular Grid array representing the same surface Z=f(X,Y) by
    an interpolation process.  X, Y and Z are arrays defined by  the  COLUMN
    command  (see  HELP COLUMN). It triangulates the data for interpolation.
    If a triangulation already  exists,  and  only  the  Z  array  has  been
    changed, RANDOM_MAP does not make a new triangulation.

    Often,  the user-provided Z=f(X,Y) surface is REGULARLY SAMPLED, even if
    NOT COMPLETELY SAMPLED. In this case, it is recommended to use  directly
    the  RGDATA  command to create a Regular-grid map, since RANDOM is known
    to perform awkwardly with regularly sampled data.

    The interpolated grid can be  defined  by  the  arguments.  If  Arg1  is
    "RGMAP",  the interpolated grid will be exactly coincident with the cur-
    rent Regular Grid array, else Arg1 and Arg2 are  used  to  indicate  the
    number of pixels in X and Y directions and Arg2 = Arg1 if not specified.
    If no argument is specified, the previous grid (if any) is  reused  (see
    also subtopic /SKIP).

    Note that several hypothesis are made about the geometry of triangles in
    the plot page space (hence the geometry may be changed by  changing  the
    LIMIT  or  the  BOX_LOCATION).  You should thus use limits which gives a
    reasonable representation of what are the neighbours  of  a  given  data
    point.  Moreover,  this  is an interpolation process. Hence if the basic
    sampling theory is not respected by your choice of input data points and
    output grid, spurious oscillations may occur in the resulting grid.


Gildas manager 2020-12-03