rasterize shape file and output as .img

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?

Another thing is that I need to output the raster as IMG (erdas/arcgis)
format.

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]]

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 at 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 at 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 at 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]]

--
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 at nhh.no

Dear Roger,

Sorry for my delay.

I still can't do that. Please, see below the steps and the error message.
I shapefile have only one polygon, and only one collumn (CoverClass).

  

reser<-readOGR(dsn=".", layer="ARN_026_214pt5m")
    

OGR data source with driver: ESRI Shapefile
Source: ".", layer: "ARN_026_214pt5m"
with  1  rows and  3  columns
Feature type: wkbPolygon with 2 dimensions
  

reser.df<-reser at data
reser.df$ClassCover<-1
reser.df<-subset(reser.df, select=c(ClassCover))
reser at data<-reser.df <reser at data%3C-reser.df>
reser at data
    

  ClassCover
0          1
  

reser.SG <- Sobj_SpatialGrid(reser)$SG

plot(reser.SG)
plot(reser, add=T, col="red")
str(reser.SG)
    

Formal class 'SpatialGrid' [package "sp"] with 5 slots
  ..@ grid       :Formal class 'GridTopology' [package "sp"] with 3 slots
  .. .. ..@ cellcentre.offset: Named num [1:2] 371506 8764564
  .. .. .. ..- attr(*, "names")= chr [1:2] "x" "y"
  .. .. ..@ cellsize         : Named num [1:2] 941 941
  .. .. .. ..- attr(*, "names")= chr [1:2] "max" "max"
  .. .. ..@ cells.dim        : int [1:2] 100 75
  ..@ grid.index : int(0)
  ..@ coords     : num [1:2, 1:2] 371506 464669 8764564 8834201
  .. ..- attr(*, "dimnames")=List of 2
  .. .. ..$ : NULL
  .. .. ..$ : chr [1:2] "x" "y"
  ..@ bbox       : num [1:2, 1:2] 371035 8764093 465139 8834672
  .. ..- attr(*, "dimnames")=List of 2
  .. .. ..$ : chr [1:2] "x" "y"
  .. .. ..$ : chr [1:2] "min" "max"
  ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slots
  .. .. ..@ projargs: chr NA
  

o <- overlay(reser, reser.SG)
o
    

     ClassCover
NA           NA
NA.1         NA
  

reser.SGDF <- SpatialGridDataFrame(slot(reser.SG, "grid"),
    

+   proj4string=CRS(proj4string(reser.SG)), data=o)
Error in validityMethod(object) :
  unequal number of objects in full grid and data slot
  


  

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] raster_0.8.9-6  maptools_0.7-20 foreign_0.8-34  rgdal_0.6-7
[5] sp_0.9-32
loaded via a namespace (and not attached):
[1] grid_2.9.0      lattice_0.17-20

Best wishes,

milton

	[[alternative HTML version deleted]]