Thanks Edzer and Hengl. It works. 
But R is really shaking when large grids are processed. We wish there is improvement of sp in the future like GIS handling grids.
 
Regards
 
Yong

________________________________

From: Edzer Pebesma [mailto:edzer.pebesma@uni-muenster.de]
Sent: Tue 20/05/2008 6:11 PM
To: Yong Li
Cc: r-sig-geo@stat.math.ethz.ch
Subject: Re: [R-sig-Geo] How to subset a spatial grid?



Have you tried

Map1 <- Map[1:100,1:100]
?

Note that this works differently for SpatialGridDataFrames and
SpatialPixelsDataFrames; the first knows about [rows,cols,bands], the
second about [pixels, bands].
--
Edzer

Yong Li wrote:
> Dear All,
>
> I want to subset a large spatial grid (2000*2000) into many smaller
> grids for further processing in my simulation models. Could anyone do it
> before and any tips will be highly appreciated?
>
> Library(rgdal)
> Map <- readGDAL("yong.img")  # one image from erdras imagine
> Map$va <- Map$band1
> Map$band1 <- NULL
> ????
> Map1 <- a subset of Map$va based on selected cols and rows.
> ????......
>
> Cheers
>
> Yong Li
>
> _______________________________________________
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> R-sig-Geo@stat.math.ethz.ch
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>  




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