[R-sig-Geo] converting raster into grid shapefile

[Alexandre VILLERS]

Hello,

I'm currently working on MODIS data. The aim is to identify through 
spectral varitions across time crop type on a large region.
For that purpose, I have the type of crop on all plots of a 500 squared 
km study area (plot locations with a max of 10 m error) as a ESRI shapefile.
I already converted MODIS data as geotif for each spectral band of 
interest with the MODIS reprojection tool (see 
http://spatial-analyst.net/wiki/index.php?title=Download_and_resampling_of_MODIS_images 
for more details). I would like to get the % of each crop under each 
pixel (250 m wide) of the raster data for further analysis.
I would know how to do that with ArcGis, given an appropriate grid 
shapefile fitted on the raster. I would so be able (I hope) to work with 
grid number to isolate the ones of interest.
Does anyone see how to create such a grid shapefile, or better, to run 
the whole stuff with R ?

Best regards

Alex

-- 

Alexandre Villers
PhD Student
Team "Biodiversity"
Centre d'Etudes Biologiques de Chizé-CNRS UPR1934
79360 Beauvoir sur Niort

Phone +33 (0)5 49 09 96 13
Fax   +33 (0)5 49 09 65 26




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