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(reser@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(reser@data$ClassCover, gride)
Error in function (classes, fdef, mtable)  :
  unable to find an inherited method for function "overlay", for signature
"numeric", "GridTopology"


On Fri, Apr 3, 2009 at 3:40 PM, Roger Bivand <Roger.Bivand@nhh.no> 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
>>
>>        [[alternative HTML version deleted]]
>>
>> _______________________________________________
>> R-sig-Geo mailing list
>> R-sig-Geo@stat.math.ethz.ch
>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>
>>
> --
> 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: Roger.Bivand@nhh.no
>
>

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