[R] diffusing GIS data in maps

Felix Andrews felix at nfrac.org
Tue Aug 14 13:21:47 CEST 2007

Package akima allows simple 2D interpolation from points to a grid.

On 8/14/07, Lawrence D. Brenninkmeyer <ldb at outsourcethinking.com> wrote:
> Hi-
> I am trying to find a way to diffuse GIS data on a European map. I have a
> dataset consisting of particular locations scattered across Europe,
> along with magnitude and value information. I can plot these as discrete
> points with something like the following:
> "geocode" is a dataframe with four columns: LAT; LONG; MAGNITUDE;VALUE.
> library(maps)
> library(mapdata)
> map("worldHires", regions=c("Germany", "Belgium", "Netherlands"))
> points(geocode$LONG, geocode$LAT, cex=geocode$MAGNITUDE / 2500,
> col=rainbow(length(geocode$VALUE), start=0, end=.4)[rank(geocode$VALUE)])
> This gives me a map of Europe with my datapoints highlighted in two ways:
> magnitude is represented by the size of the point, and value is
> represented by the color.
> However, what I would really like is for there to be some sort of
> diffusion, such that instead of discrete points, the European map is
> covered in color so I can see more clearly whether there are regional
> patterns (something that will presumably look like this contour chart:
> <http://addictedtor.free.fr/graphiques/RGraphGallery.php?graph=20>  only
> on the European map).
> I have absolutely no idea where to start because I can't find a function
> that will allow me to diffuse the datapoints on a map.
> thank you for any help
> ldb
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Felix Andrews / 安福立
PhD candidate
Integrated Catchment Assessment and Management Centre
The Fenner School of Environment and Society
The Australian National University (Building 48A), ACT 0200
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