It turns out when doing raster calculations that the default output being
created by ArcGIS was an image (ERDAS IMAGINE) and not a GRID after all.
 This was not immediately apparent until going back a step, though I am very
glad to have finally noticed it.  My apologies; I guess this is something to
look out for in future.

Tyler


On Wed, Nov 10, 2010 at 8:12 PM, Robert J. Hijmans <r.hijmans@gmail.com>wrote:

> Well, GDALinfo in the latest 'rgdal' does in fact return the
> attributes table, upon request, and 'raster' does request it (Roger
> implemented this last week). You can see it (if it exists) when you do
> print(x) with a RasterLayer (and when using the latest rgdal and
> raster). But I have not (consciously) done anything with this that
> might change how values are returned. So I think (hope) it has nothing
> to do with this. What are your versions  ( sessionInfo() ) ? I may
> need to see the arc grid file or a small subset of it. Can you read
> the values correctly with rgdal ?
> Robert
>
> On Wed, Nov 10, 2010 at 4:54 PM, Michael Sumner <mdsumner@gmail.com>
> wrote:
> > What are the kinds of values that you  see in ArcGIS?  Is this an ADF
> > raster, i.e. a folder of many files like "w000001.adf" etc. ?
> >
> > This is a just a guess, so sorry if it's off-base - I don't know of
> > any non-ESRI tool to get at these values.
> > If this is an ADF raster I know that you won't be able to access the
> > descriptive/categorical values you would use in Arc, you'll just get
> > the underlying integer index.  (BTW, this lookup type with an
> > underlying integer mapped to a 'descriptive value' is like the factor
> > type in R - does that sound like what you have?).
> >
> > The raster is read via the GDAL library, which does not provide the
> > "categorical values" you assign in Arc. It's just a part of the format
> > that hasn't been reverse engineered by the GDAL developers, but
> > further, if your descriptive values are actually text then GDAL cannot
> > represent them - only numeric types are supported, even though the
> > rasters in R can have text/character types.
> >
> > Cheers, Mike.
> >
> > On Thu, Nov 11, 2010 at 11:35 AM, Tyler Dean Rudolph
> > <tylerdeanrudolph@gmail.com> wrote:
> >> I have a pretty simple code to extract cell values from a habitat map
> >> (RasterLayer) based on xy coordinates.  I recently updated habitat
> >> information with a new raster image but for some reason now when I read
> in
> >> the values it's as though they are no longer being interpreted as
> discrete
> >> values, so instead of select, discrete classes I am getting new
> arbitrary
> >> groupings that I didn't create.  The input file is a standard
> >> ArcGIS-configured GRID raster layer.  The attribute table in
> ArcCatalogue
> >> displays the data as expected, and I've ensured the raster has been
> classed
> >> as containing discrete values prior to opening it in R.
> >>
> >> Perhaps something in the packages have changed since I ran this last?
>  I'm
> >> currently trying to assess in the raster documentation what kind of
> >> additional arguments I might have at my disposal in order to clarify how
> I
> >> want the data to be read....
> >>
> >> Tyler
> >>
> >>        [[alternative HTML version deleted]]
> >>
> >> _______________________________________________
> >> R-sig-Geo mailing list
> >> R-sig-Geo@stat.math.ethz.ch
> >> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >>
> >
> >
> >
> > --
> > Michael Sumner
> > Institute for Marine and Antarctic Studies, University of Tasmania
> > Hobart, Australia
> > e-mail: mdsumner@gmail.com
> >
> > _______________________________________________
> > R-sig-Geo mailing list
> > R-sig-Geo@stat.math.ethz.ch
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >
>

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