[R-sig-Geo] Polygons VS MultiLineString

[Frede Aakmann Tøgersen]

Well, since the workhorse behind the rasterToContour() function is contourLines() from the lattice package don't expect the contour lines for a given level to form a single well defined polygon (the definition of which of course needs to be specified).

Try this:

f <- system.file("external/test.grd", package="raster")
r <- raster(f)
x <- rasterToContour(r)
class(x)
str(x)

## the levels
levels(x at data$level)

plot(r)

plot(subset(x, level == 400), add=TRUE)

plot(subset(x, level == 200), add=TRUE)

Yours sincerely / Med venlig hilsen


Frede Aakmann Tøgersen
Specialist, M.Sc., Ph.D.
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> -----Original Message-----
> From: R-sig-Geo [mailto:r-sig-geo-bounces at r-project.org] On Behalf Of
> Michael Sumner
> Sent: 4. marts 2015 09:11
> To: Antonio Rodriges; r-sig-geo at r-project.org
> Subject: Re: [R-sig-Geo] Polygons VS MultiLineString
> 
> Try gPolygonize from rgeos, but it *really* depends on whether your lines
> close cleanly.
> 
> On Wed, 4 Mar 2015 18:38 Antonio Rodriges <antonio.rrz at gmail.com>
> wrote:
> 
> > Hello,
> >
> > I use "rasterToContour" to derive isolines for raster. After that I
> > save them as GeoJSON (or ESRI Shapefile). However, it saves contours
> > as "MultiLineString"
> >
> > Is it possible to save "contours" as "Polygons"?
> >
> > Code:
> >
> > to_c - is a raster
> > contours <- rasterToContour(to_c, levels = c(18, 33))
> > writeOGR(contours, "file.js", layer="", driver="GeoJSON")
> >
> > _______________________________________________
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> > R-sig-Geo at r-project.org
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >
> 
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