NAME

       SHGETNP - find the nearest points to a specified point in 3-space.

SYNOPSIS

       CALL SHGETNP (PX, PY, PZ, N, X, Y, Z, IFLAG, IWK, RWK, NP, IER)

DESCRIPTION

       PX          (real,input) The X coordinate value for a point P whose nearest neighbor is to
                   be found.

       PY          (real,input) The Y coordinate value for a point P whose nearest neighbor is to
                   be found.

       PZ          (real,input) The Z coordinate value for a point P whose nearest neighbor is to
                   be found.

       X           (real, input) An array containing the X coordinates of the input data points.

       Y           (real, input) An array containing the Y coordinates of the input data points.

       Z           (real, input) An array containing the Z coordinates of the input data points.

       IFLAG       (integer, input) A flag that equals 0 if  this  is  the  first  call  to  this
                   subroutine for the given dataset and equals 1 otherwise.

       IRK         (integer, input) An integer workspace dimensioned for at least 2*N.

       RWK         (real, input) A real workspace dimensioned for at least 11*N+6.

       NP          (integer,  output) An index such that (X(NP),Y(NP),Z(NP)) is the nearest input
                   data point to P. NP = 0 if IER .NE. 0. On successive calls to this  subroutine
                   after  the  first (that is when IFLAG=1) you can find the Mth closest point to
                   (PX,PY,PZ) with the Mth call. IWK and RWK should not be modified between calls
                   to SHGETNP if you are wanting to find successive nearest neighbors.

       IER         (integer,  output)  An  error  return value.  If IER is returned as 0, then no
                   errors were detected. If IER is non-zero, then  refer  to  the  man  page  for
                   shgrid_errors for details.

USAGE

       SHGETNP  is  called to find the nearest point to a specified point in 3-space.  Successive
       calls to SHGETNP will determine the point nearest the specified  point  exclusive  of  the
       points  found  in  previous calls, i.e. successive calls can be used to find the N nearest
       points for any N between one and the maximum number of points in the input dataset.

ACCESS

       To use SHGETNP, load the NCAR Graphics library ngmath.

SEE ALSO

       shgrid, shseti, shgeti, shgrid_params.

       Complete documentation for Shgrid is available at URL
       http://ngwww.ucar.edu/ngdoc/ng/ngmath/shgrid/shhome.html

COPYRIGHT

       Copyright (C) 1997-2000
       University Corporation for Atmospheric Research

       The use of this Software is governed by a License Agreement.