NCL > Application examples > Basic examples

Ngmath example 3

How to retrieve aspects and slopes of an interpolation

This example can be created using HLU C and FORTRAN library calls or NCL. It demonstrates how to use the Natgrid package to calculate slopes and aspects of a simple interpolation using natural neighbor interpolation (Natgrid is part of the Ngmath library). The names of the source files for this example are nm03c.c, nm03f.f, and nm03n.ncl.


This module discusses how to use the Natgrid package using calls to the Ngmath library and the HLU library. Some of the resources are controlled through a resource file called nm03.res.

Creating the plot using HLUs

The HLU C program that generates this plot is called nm03c.c.

Creating the plot using HLU FORTRAN library calls

The HLU FORTRAN program that generates this plot is called nm03f.f.

Creating the plot using NCL

The NCL script that generates this plot is called nm03n.ncl.

The data

This plot does not use any external data.

How to run this example

This example can be generated using a C program (nm03c.c), a FORTRAN program (nm03f.f), or an NCL script (nm03n.ncl). The examples are installed in the following locations:

  • $NCARG_ROOT/lib/ncarg/hluex/ngmath/nm03c.c
  • $NCARG_ROOT/lib/ncarg/hluex/ngmath/nm03f.f
  • $NCARG_ROOT/lib/ncarg/nclex/ngmath/nm03n.ncl
The resource file for this example is located in:

  • $NCARG_ROOT/lib/ncarg/resfiles/ngmath/nm03.res
You can copy this example and run it by typing "ng4ex nm03c", "ng4ex nm03f", or "ng4ex nm03n". A copy of the source file and resource file will be placed in your current working directory. The source code will be compiled and automatically run for you.

working directory and run through NCL for you.