how to mask a raster with a coarser resolution selected grid squares ?

Dear listers,

Thanks to Robert and Edzer I finally found a way to do this. This is the
final solution I got to, in case anybody wants to use it:

##############################################
# This function returns a masks all zones of a 1km raster which
# do not fall inside 10km grid cells defined by a list of selected
# 10km-resolution cell centers. cell.centers must be a 
SpatialPointsDataFrame
##############################################
maskFromCoarserResolution <- function(r.1km, cell.centers.10k){
   fr1k <- paste(dirRefCarto,"catalonia_utm1k.asc",sep="")
   r1k <- raster(fr1k)
   r10k <-  aggregate(raster(r1k), 10)
   cells <- cellFromXY(r10k, cell.centers.10k)
   r10k[] <- NA
   r10k[cells] <- 1
   r10kto1k <- disaggregate(r10k, 10)
   extent.r1k <- extent(r1k)
   #in order to make sure both bounding boxes are equal
   r10kto1k <- crop(r10kto1k, extent.r1k)
   r1k.masked <- mask(r1k, r10kto1k)
}

Arnald Marcer
CREAF

Dear listers,

Can anybody help me with this ?

How can I mask a 1km UTM grid raster with a list of coordinates
which represent the center of 10km UTM grid squares ? Ultimately
I want the 1km grid raster with only the pixels that fall inside
the 10km UTM grid squares.

Also, how can I build a SpatialPolygonsDataFrame representing 10km
UTM grid squares from a list of coordinates which represent their grid
center.

I will appreciate if you can give me some hints on how to do this.

Arnald Marcer
CREAF

-----------------------------------------------------------------
Arnald Marcer
Investigador

Centre de Recerca Ecol?gica i Aplicacions Forestals (CREAF)
Universitat Aut?noma de Barcelona
08193 Barcelona

Tel: 93 5811312
Fax: 93 5814151
-----------------------------------------------------------------
Arnald Marcer
Researcher

Centre for Ecological Research and Forestry Applications (CREAF)
Autonomous University of Barcelona
08193 Barcelona

Phone: +34 93 5811312
Fax:   +34 93 5814151