On Fri, 3 Apr 2009, milton ruser wrote:
Hi Roger,
I think I am making something wrong (see the error message, please).
reser is the polygon object that I read from a shapefile.
Thanks for your time.
milton
class(reser)
[1] "SpatialPolygonsDataFrame"
attr(,"package")
[1] "sp"
head(re...@data)
DOCNAME area_ha ClassCover
22 JRN-720 - 271,0m 8022.687 1
reser.bbox<-bbox(reser)
resolution<-c(60,60) #meters
#GridTopology(cellcentre.offset, cellsize, cells.dim)
ccoffset<-c(reser.bbox[,1])
cdim<-round((reser.bbox[,2]-reser.bbox[,1])/resolution[1],0)+1
gride<-GridTopology(ccoffset, resolution, cdim)
str(gride)
Formal class 'GridTopology' [package "sp"] with 3 slots
..@ cellcentre.offset: Named num [1:2] 283916 8578881
.. ..- attr(*, "names")= chr [1:2] "r1" "r2"
..@ cellsize : num [1:2] 60 60
..@ cells.dim : int [1:2] 313 1280
overlay(re...@data$classcover, gride)
Error in function (classes, fdef, mtable) :
unable to find an inherited method for function "overlay", for signature
"numeric", "GridTopology"
Try SpatialGrid(gride) instead - look at getMethods(overlay) if it helps
(it may not, there are many methods). Also see the thread on this list (a
reply: http://finzi.psych.upenn.edu/R/Rhelp08/2009-February/005049.html).
RSiteSearch("rasterize") does help.
Roger
On Fri, Apr 3, 2009 at 3:40 PM, Roger Bivand <[email protected]> wrote:
On Fri, 3 Apr 2009, milton ruser wrote:
Dear all,
I have a set of shapefile and I need rasterized it using a collumn called
ClassCover,
and with the resolution of 30 meters. How can I do this on R?
Use bbox() of the SpatialPolygonDataFrame to find the extent. Create a
GridTopology object, and overlay the polygons - possibly just with
ClassCover - and the SpatialGrid built with the GridTopology object. This
should yield a SpatialGridDataFrame with a single band, with NAs outside the
polygons, and the polygon column values for raster cells where their centres
fall inside the polygons.
Another thing is that I need to output the raster as IMG (erdas/arcgis)
format.
writeGDAL in rgdal.
Hope this helps,
Roger
Any help are welcome.
Best wishes,
milton
Brasil/Toronto
require(maptools)
require(sp)
require(rgdal)
todos<-readShapePoly("myshape.shp")
sessionInfo()
R version 2.9.0 alpha (2009-03-26 r48224)
i386-pc-mingw32
locale:
LC_COLLATE=English_Canada.1252;LC_CTYPE=English_Canada.1252;LC_MONETARY=English_Canada.1252;LC_NUMERIC=C;LC_TIME=English_Canada.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] rgdal_0.6-7 maptools_0.7-20 sp_0.9-32 foreign_0.8-34
loaded via a namespace (and not attached):
[1] grid_2.9.0 lattice_0.17-20
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--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: [email protected]
--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: [email protected]
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