[R-sig-Geo] rasterize in parrallel

[Jérome Mathieu]

Dear all,

I need to rasterize the same shapefile according to different fields stored
in the @data of the shapefile. So I need to loop trough the fields (named
sc1 to sc27) to rasterize upon each field. With a regular sequential loop
it takes a very long time (much longer than in ArcMap), so I would like to
parallelize it, but I didn't succeed so far.

I tried :

# read shapefile
 library(maptools)
 polyg<-readShapePoly("D:\\polyg.shp")
 polyg at proj4string <- CRS("+init=epsg:2154")

library(doParallel)
cl <- makeCluster(4)
registerDoParallel(cl)

grain<-50
nsc<-4

foreach(idxsc = 1 : nsc , .packages="raster", polyg=polyg) %dopar% {

eval(parse(text=paste("RRpolyg_",idxsc,"<-raster(polyg,res=c(grain,grain))",sep="")))
# create raster template
eval(parse(text=paste("projection(RRpolyg_",idxsc,") <-
proj4string(polyg)",sep="")))      # projection
eval(parse(text=paste("RRpolyg_",idxsc,"<-rasterize(polyg,RRpolyg_",idxsc,",field=polyg at data$sc",idxsc,")",sep="")))
# rasterization

}

stopCluster(cl)

and I get the following error :

Error in { :
  task 1 failed - "unable to find an inherited method for function 'raster'
for signature '"numeric"'"


the data are here

http://we.tl/7qqegfLoBA


Any help would be greatly appreciated !

Jerome


> sessionInfo()
R version 3.1.3 (2015-03-09)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

locale:
[1] LC_COLLATE=French_France.1252  LC_CTYPE=French_France.1252
LC_MONETARY=French_France.1252 LC_NUMERIC=C
LC_TIME=French_France.1252

attached base packages:
[1] parallel  stats     graphics  grDevices utils     datasets  methods
base

other attached packages:
 [1] rgeos_0.3-11     rgdal_0.9-2      maptools_0.8-36  lattice_0.20-31
foreign_0.8-63   raster_2.3-40    sp_1.1-0         doParallel_1.0.8
iterators_1.0.7  foreach_1.4.2

loaded via a namespace (and not attached):
[1] codetools_0.2-11 compiler_3.1.3   grid_3.1.3       tools_3.1.3







-- 
Jérôme Mathieu
Université Pierre & Marie Curie
Institute of Ecology and Environmental Science (Paris)

Bât. A - 7ème Etage, porte 715
7 quai St.-Bernard
F-75252 Paris Cedex 05

tel: 01 44 27 34 22

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