Message-ID: <1430485336885-7588149.post@n2.nabble.com>
Date: 2015-05-01T13:02:16Z
From: sadaoui
Subject: Delimit a polygon for the region which is> 1000 m from my raster altitude
In-Reply-To: <D1680198.12746D%macqueen1@llnl.gov>
Thank you very much "MacQueen, Don" for your answer.
I have followed your instructions from this script :
library(raster)
library(sp)
f <- system.file("external/test.grd", package="raster")
r <- raster(f)
# add contour
x <- rasterToContour(r,levels=500)
class(x)
plot(r)
plot(x, add=TRUE)
#export contour to shapefile
library(rgdal)
writeOGR(x, ".", "contour", driver="ESRI Shapefile")
but when I open the shapefile, is a lines not a polygons? My goal is to
have the polygon areas for altitude> 500m.
I thought to "rasterToPolygons"
library(raster)
library(sp)
f <- system.file("external/test.grd", package="raster")
r <- raster(f)
# add polygon
library(rgeos)
pol <- rasterToPolygons(r, fun=function(x){x>500})
plot(pol, add=T, col='red')
#export polygon to shapefile
library(rgdal)
writeOGR(pol, ".", "polygon", driver="ESRI Shapefile")
but the result, it displays a shapefile with polygons for each pixel
I just want a polygons to areas where are> 500m, not for each pixel.
Thank you again
--
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