[R-sig-Geo] Creating polygons out of an irregular data set to represent specific classes

Sébastien Durand v8extra at gmail.com
Fri Dec 3 02:08:44 CET 2010

Hello to all,

I have struggling with R for at least a weak and I guess I do really need your help figuring this out.

I have to work with a large data set (thousands of points) and to create figures that are small and good looking for publications.

You can probably suggest me a slick a working way to approach this problem. 

I would really appreciate.

Let say we start with:

ak.li=interp(akima$x, akima$y, akima$z, xo=seq(min(akima$x), max(akima$x), length = dimgrid),yo=seq(min(akima$y), max(akima$y), length = dimgrid),linear = TRUE, extrap=FALSE, duplicate = "mean")

# Now I have the regular grid. 

 cLines = contourLines(x = ak.li$x, y = ak.li$y, z = ak.li$z, nlevels = 7)

# Now I have the contours...

That is from that point on that I cannot find a solution.

I tough of selecting all the image data and converting it a specific class value, but then I still get stuck into the same issue I dont know how to convert those pixel into polygons.

# ...

I do need guidance...

Thanks a lot!


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