Importing subsets of an ASCII file

I have yet to find a computer robust enough to import my landscape-level
habitat data in one foul swoop (835 MB).  I tell myself once I do succeed I
can save it as an R object, at which point it will be much smaller and
easier to handle, but it seems another option that may be possible is to
specify the x and y ranges of the SpatialGrid or im file I want to
import within the import call itself, which would ideally make it easier to
process for the average machine, at which point I could simply run a loop of
sorts to progressively extract data for the various subregions of my study
area.

Now I've been pouring over the archives and it seems to me that earlier I
ran across an option within some ascii import function where the x and y
ranges can be specified.  Does this ring a bell for anyone?  It might be
just the ticket in this type of situation.  The tif file is even bigger so
that won't work and I'm not clear on what else would at the moment.

Tyler

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