[R-sig-Geo] change projection of large raster file

[Carsten Dormann]

Dear all,

I want to compute equal-area grid values for global land cover (GLC2000 
data). The equal-area grid is in Mollweide projection.

I use raster to read the GLC-data. Now I want to project these 
WGS84-projected GLC-data into Mollweide.

Even after 24 hours of computing, R was still milling away. I regard 
this as a problem, rather than a consequence of the large data set (54 
MB). Correctly so?

Any hints on how to do this correctly appreciated!

[Only in case you were wondering WHY I do this: The next steps will be 
to simplify down to only one category (using data == "1") and then use 
"aggregate" to actually sum the number of positive pixels in each cell. 
I did the whole thing with a 1-degree grid without any problems (taking 
roughly 30min for each class).]


Cheers,

Carsten


R-code:

r <- raster(grid100) # to convert the SpatialGrid into a raster
test <- raster("glc2000_v1_1") #reads the GLC data
ex <- projectExtent(test, CRS(proj4string(grid100))) # reprojects the extent
setOptions(chunksize = 1e+04, maxmemory = 1e+06)
# based on comment in: 
https://r-forge.r-project.org/forum/message.php?msg_id=4025&group_id=294
test2 <- projectRaster(test, ex) # to project the actual GLC-data


sessionInfo()

R version 2.13.0 RC (2011-04-05 r55311)
Platform: i386-apple-darwin9.8.0/i386 (32-bit)

locale:
[1] de_DE.UTF-8/de_DE.UTF-8/C/C/de_DE.UTF-8/de_DE.UTF-8

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

other attached packages:
[1] maptools_0.8-6  lattice_0.19-26 foreign_0.8-44  rgdal_0.6-33 
raster_1.8-12   sp_0.9-80

loaded via a namespace (and not attached):
[1] grid_2.13.0  tools_2.13.0





-- 
Dr. Carsten F. Dormann
Department of Computational Landscape Ecology
Helmholtz Centre for Environmental Research-UFZ	
(Department Landschaftsökologie)
(Helmholtz Zentrum für Umweltforschung - UFZ)
Permoserstr. 15	
04318 Leipzig				
Germany

Tel: ++49(0)341 2351946
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