[R-sig-Geo] GRASS and R question

Jonathan Greenberg jgreenberg at arc.nasa.gov
Sun Sep 10 00:22:43 CEST 2006

I was wondering if I could get some brief feedback on exactly what are the
capabilities of the sp and spgrass6 -- say I'd like to use R to calculate
and NDVI image (I know GRASS's mapcalc can do this fine, but I'm thinking of
some more complicated analyses that aren't easily performed in R and I
figured if I can figure out NDVI I can figure out the rest of them) -- Does
sp, spgrass6 and R itself provide both the data ingestion capabilities as
well as the necessary subsetting capabilities if my file is very large (e.g.
Can R do a per-pixel or per-line read/process/write routine, or will it
attempt to load an entire raster into memory)?

If R can deal with import of a multiband image and tiled processing, can
someone here perhaps post an example of how to accomplish the above task
(taking a 4 band large file, calculating NDVI and then writing out the NDVI
to disk) using R?  Thanks!


Jonathan A. Greenberg, PhD
NRC Research Associate
NASA Ames Research Center
MS 242-4
Moffett Field, CA 94035-1000
Office: 650-604-5896
Cell: 415-794-5043
AIM: jgrn307
MSN: jgrn307 at hotmail.com

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