NAME

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

FUNCTION PROTOTYPE

       int c_shgetnp(float, float, float, int, float *, float *, float *,
                     int, int *);

SYNOPSIS

       int c_shgetnp (px, py, pz, n, x[], y[], z[], iflag, ier );

DESCRIPTION

       px          (float)  The  X coordinate value for a point P whose nearest neighbor is to be
                   found.

       py          (float) The Y coordinate value for a point P whose nearest neighbor is  to  be
                   found.

       pz          (float)  The  Z coordinate value for a point P whose nearest neighbor is to be
                   found.

       n           (int) The number of input data points, n > 1.

       x           (float) An array of length n containing the X coordinate values for the  input
                   data points.

       y           (float)  An array of length n containing the Y coordinate values for the input
                   data points.

       z           (float) An array of length n containing the Z coordinate values for the  input
                   data points.

       iflag       (int)  A  flag  that equals 0 if this is the first call to this subroutine for
                   the given dataset and equals 1 otherwise.

       ier         (pointer to int) An error return value.  If *ier is returned  as  0,  then  no
                   errors  were  detected.  If  *ier  is  non-zero, then look at the man page for
                   shgrid_errors for details.

USAGE

       c_shgetnp is called to find the nearest point to a specified point in 3-space.  Successive
       calls  to  c_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.

       c_shgetnp  returns  an integer, say np, such that (x[np],y[np],z[np]) is the nearest input
       data point to P. np = -1 if *ier is not zero. On successive calls to this  function  after
       the first (that is when iflag=1) you can find the Mth closest point to (px,py,pz) with the
       Mth call.

ACCESS

       To use c_shgetnp, load the NCAR Graphics library ngmath.

SEE ALSO

       shgetnp, c_shgrid, c_shseti, c_shgeti, shgrid_params.

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

COPYRIGHT

       Copyright (C) 2000
       University Corporation for Atmospheric Research

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