ncl_nnalg man page

nnalg — a tool for displaying features of the Natgrid algorithm


nnalg algorithmic_data_file


"nnalg" takes a single argument which is a the name of a special file created by the Fortran subroutine NATGRIDS or the C function c_natgrids in the Natgrid package. This file  contains data appropriate for displaying various features of the Natgrid algorithm. By default, this file is not created. In order to create it, you need to set the parameter adf in the Natgrid package.  You can additionally override the default file name of "nnalg.dat" by using the parameter alg.

To invoke "nnalg", simply type the command:

nnalg data_file

By editing the data file, you have many options as to what is displayed and what the appearance of the plot looks like.

The features that can be displayed are:

 1. The input data points
 2. The natural neighbor circumcircles
 3. The Delaunay triangulation, derived from the natural
    neighbor circumcircles
 4. The Voronoi polygons
 5. The first order natural neighbors of a given
    input point (or points)
 6. The second order natural neighbors of a given input
    point (or points)

The first four items in the above list are displayed in the default case.


What gets displayed by nnalg depends on values in the input data file which can be changed by manual editing.

See Also


Complete documentation for nnalg is available at URL


March 1997-1998 UNIX NCAR GRAPHICS