[R] Isocontour-lines of spatial data on a rectangular grid (not plots!)

[rohan sadler]

Hi Dieter,

The "sm" (smoothing methods library) of Bowman and Azzalini (Bowman, AW 
& Azzalini A (1997) Applied Smoothing Techniques for Data Analysis: The 
Kernel Approach with S-Plus Illustrations, Clarendon Press, Oxford).

Check out pages 9 and 10 (Figure 1.8).

I don't know how large is large for you as a data set, so I can't say 
how well it goes. I would say it goes as well as anything else.

Rohan Sadler

Dieter Menne wrote:

>Dear R-Listers,
>
>I have spatial data on an equidistant rectangular grid, similar to
>topographic data. I know that there are quite a few R-packages or base
>functions that provide nice iso-contours plot, but I don't want a plot, just
>the smoothed isocontour line of ONE level (e.g. 10 mm).
>
>Data sets are large, so it would be preferable if the availability of
>regular grid data could be exploited, and the fact that I only need ONE
>isocontour line.  Polynomial fits are not adequate, but loess works nicely
>for the plots. Akima/interp might be a little too general, and if I remember
>Brian Ripley's comments correctly, the coefficients are "only for internal
>use".
>
>Can someone suggest me a package?
>
>
>Dieter Menne
>
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