[SciPy-user] problem using interp2d

Fred Clare fred at ucar.edu
Fri Aug 26 13:10:16 CDT 2005

We would like to fill in a little history of the Natgrid
function in NCAR Graphics.  Natgrid is based on Dave
Watson's original code "nngridr."  "nngridr" was written
in C as a stand-alone interactive application - it asked
for input from standard input and produced output to
standard output.  In the mid 1990s we contacted
Dr. Watson about whether he would give permission
for us to adapt "nngridr" to make it a function call and
incorporate that into our packages, with permission
to redistribute.  The deal he gave us was that
he would allow this under the conditions:

    1.)  We purchase his book "nngridr - An Implementation of
         Natural Neighbor Interpolation" (which he published privately).
    2.)  We call the function something other than "nngridr."
    3.)  We provide adequate documentation.

He gave this permission in the interests of having natural
neighbor algorithms reach a wider audience.

Our first release of Natgrid, with Fortran and C interfaces,


was in 1996 as part of the Ngmath library.

Subsequently, an NCL version was implemented:


and more recently a Python interface was provided as part of
our PyNGL package:


An example of the Python interface to Natgrid can be found at
in one of the PyNGL tutorial examples at:


The e-mail addresses and web sites we referenced in
dealing with Dr. Watson are no longer in service.

Watson's book, "Contouring: A Guide to the Analysis and Display
of Spatial Data" (which is really a book about interpolation
methods) is still available from Amazon:


Fred Clare
fred at ucar.edu

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