polygons from pixels.

Dear RGeo-Gurus,

I have a ASC file, and would like that each pixel come to be a polygon.
Any help are welcome.

require(rgdal)
require(adehabitat)

(file1 <-  paste(system.file(package = "adehabitat"),
              "ascfiles/elevation.asc", sep = "/"))
el <- readGDAL(file1)
image(el, axes=T)

Something like this is in sp:

el1 <- as(el, "SpatialPixelsDataFrame")
el2 <- as(el1, "SpatialPolygons")
IDs <- sapply(slot(el2, "polygons"), function(x) slot(x, "ID"))
df <- as(el1, "data.frame")
row.names(df) <- IDs
el3 <- SpatialPolygonsDataFrame(el2, data=df)
spplot(el3, "band1", col.regions=heat.colors(20))

The actual coercion is from SpatialPixels to SpatialPolygons, so the data 
need to be put back in.

Roger

best wishes,

miltinho astronauta
brazil

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