[R-sig-Geo] Polygons VS MultiLineString

[Mathieu Rajerison]

Hello,

My advice is : why don't you reclass your raster in categories according to
raster values intervals, then you polygonize your reclassified raster ?

It would be simpler and you would have a topologically correct layer.

That's the way I do it with GRASS but you all the functions also are
included in the raster package.

Mat



2015-03-09 12:44 GMT+01:00 Antonio Rodriges <antonio.rrz at gmail.com>:

> The solution I've devised so far
>
> contours <- rasterToContour(to_c, levels = c(18, 33))
>
> res <- lapply(slot(contours, "lines"), function(x) lapply(slot(x,
> "Lines"), function(y) slot(y, "coords")))
> polies <- lapply(res, function (x) lapply(x, function (y) Polygon(y)))
> pp_18 <- Polygons(polies[[1]], ID = "18")
> pp_33 <- Polygons(polies[[2]], ID = "33")
> all_pp<- SpatialPolygons(c(pp_18, pp_33))
> df <- data.frame(value = c(18, 33), row.names = c("18", "33"))
> SPDF <- SpatialPolygonsDataFrame(all_pp, df)
>
> writeOGR(SPDF, jsfile, layer="", driver="GeoJSON")
>
> This is in case you have only two values 18 and 33. If you have more,
> create list and create Polygons also using lapply or for loop
>
> 2015-03-05 11:49 GMT+03:00 Antonio Rodriges <antonio.rrz at gmail.com>:
> > Mike,
> >
> > Thank you, that was a great example; I reproduced it.
> >
> > However, if I am satisfied with the rasterToContour output, I think
> > there should be a way to directly convert it polygons. I am seeking
> > this method.
>
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