[R-sig-Geo] calculate raster values based on vector regions

[Tomislav Hengl]

My appologies. The previous script had few (5) typos:

> library(rgdal)
> library(RSAGA)
# load the gridded map:
> rastermap <- readGDAL("rastermap.asc")
> rsaga.esri.to.sgrd(in.grids=" rastermap.asc", out.sgrds=" rastermap.sgrd", in.path=getwd())
# convert the polygon map to a raster map:
> cellsize <- rastermap at grid@cellsize[1]
> rsaga.get.usage(lib="grid_gridding", module=3)
> rsaga.geoprocessor(lib="grid_gridding", module=3, param=list(GRID="polygons.sgrd",
INPUT="polygons.shp", FIELD=1, LINE_TYPE=0, USER_CELL_SIZE=cellsize,
USER_X_EXTENT_MIN=rastermap at bbox[1,1]+cellsize, USER_X_EXTENT_MAX=rastermap at bbox[1,2]-cellsize,
USER_Y_EXTENT_MIN=rastermap at bbox[2,1]+cellsize, USER_Y_EXTENT_MAX=rastermap at bbox[2,2]-cellsize))
> rsaga.sgrd.to.esri(in.sgrds="polygons.sgrd", out.grids="polygons.asc", out.path=getwd(), prec=0)
> rastermap$polygons <- as.factor(readGDAL("polygons.asc")$band1)
# summary statistics per polygon class:
> raster.polygons <- boxplot(band1 ~ polygons, rastermap at data, col=rainbow(length(levels(rastermap
$polygons))))
> str(raster.polygons)

HTH

Tom Hengl
http://spatial-analyst.net 


> -----Original Message-----
> From: r-sig-geo-bounces at stat.math.ethz.ch [mailto:r-sig-geo-bounces at stat.math.ethz.ch] On Behalf
> Of Tomislav Hengl
> Sent: Wednesday, January 28, 2009 9:56 AM
> To: r-sig-geo at stat.math.ethz.ch
> Cc: Alexander.Herr at csiro.au
> Subject: Re: [R-sig-Geo] calculate raster values based on vector regions
> 
> 
> Dear Herry,
> 
> If I understand what you problem, one solution is to use R+SAGA. You should first convert the
> polygon map to the same grid, and then you can load it to R and do any type of aggregation:
> 
> > library(maptools)
> > library(rgdal)
> > library(RSAGA)
> # load the gridded map:
> > rastermap <- readGDAL("rastermap.asc")
> # load the shapefile:
> > rsaga.esri.to.sgrd(in.grids=" rastermap.asc", out.sgrds=" rastermap.sgrd", in.path=getwd())
> # convert the polygon map to a raster map:
> > cellsize <- rastermap at grid@cellsize[1]
> > rsaga.geoprocessor(lib="grid_gridding", module=3, param=list(GRID="polygons.sgrd",
> INPUT="polygons.shp", FIELD=1, LINE_TYPE=0, USER_CELL_SIZE=cellsize,
> USER_X_EXTENT_MIN=rastermap at bbox[1,1]+cellsize, USER_X_EXTENT_MAX=rastermap at bbox[1,2]-cellsize,
> USER_Y_EXTENT_MIN=rastermap at bbox[2,1]+cellsize, USER_Y_EXTENT_MAX=rastermap at bbox[2,2]-cellsize))
> > rsaga.sgrd.to.esri(in.sgrds="polygons.sgrd", out.grids="polygons.asc", out.path=getwd(), prec=0)
> > rastermap$polygons <- as.factor(readGDAL("polygons.asc"))
> # summary statistics per polygon class:
> > raster.polygons <- boxplot(band1 ~ polygons, rastermap @data,
> col=rainbow(length(levels(negotingrid$SOIL))))
> > str(raster.polygons)
> 
> You will of course need to adjust the "FIELD" position in the attribute table and the precision
> "prec".
> 
> To obtain and use SAGA, check this article:
> http://spatial-analyst.net/wiki/index.php?title=Software
> 
> cheers,
> 
> How is the weather now in Canberra? In Amsterdam is freezing brrr.
> 
> T. Hengl
> 
> 
> > -----Original Message-----
> > From: r-sig-geo-bounces at stat.math.ethz.ch [mailto:r-sig-geo-bounces at stat.math.ethz.ch] On Behalf
> > Of Alexander.Herr at csiro.au
> > Sent: Wednesday, January 28, 2009 2:10 AM
> > To: r-sig-geo at stat.math.ethz.ch
> > Subject: [R-sig-Geo] calculate raster values based on vector regions
> >
> >
> > Hi List,
> >
> > How would I go about assigning values to a raster based on polygon regions in R. Examples would
> be
> > most appreciated.
> >
> > I have (vector) regions assigned to a specific value. The raster has NAs and some pixels where
> > these values are likely to occur on ground. I need to assign these values to the raster and can
> do
> > this in ArcInfo through vectors and rasterizing but only to a limited raster size. And R is much
> > more preferable anyway...
> >
> > Any help appreciated.
> > Cheers
> > Herry
> >
> > _______________________________________________
> > R-sig-Geo mailing list
> > R-sig-Geo at stat.math.ethz.ch
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> 
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