[GRASS-dev] Re: Problem when loading GRASS 6 raster with large integer values into R via r.out.bin

[Rainer M Krug]

On Wed, Sep 17, 2008 at 10:49 AM, Roger Bivand <Roger.Bivand at nhh.no> wrote:
> Markus Neteler <neteler <at> osgeo.org> writes:
>
>>
>> On Tue, Sep 16, 2008 at 6:50 PM, Rainer M Krug <r.m.krug <at> gmail.com> wrote:
>> > Hi
>> >
>> > I have a problem with importing raster maps of type CELL into R -
>> > larger values become "wrapped" around as r.out.bin saves the raster
>> > values as shortint values. Is there any possibility to change that
>> > behaviour, or at least convert the exported values automatically from
>> > integer to float?
>>
>> My suggestion to Roger was to change to r.out.gdal:
>>  http://lists.osgeo.org/pipermail/grass-stats/2008-June/000799.html
>>
>> Since the GRASS-R interface knows the GRASS version it could be
>> conditionalized upon GRASS >= 6.3.0 for r.out.gdal, r.out.bin otherwise.
>
> The actual suggestion was not to use r.out.gdal, but to use the GRASS GDAL
> plugin if present. Then readRAST6() would use readGDAL() to read the
> raster directly if possible, using the GRASS plugin driver. This avoids
> creating a temporary file, but could be used directly from readGDAL() -
> it just sets up the correct path and file name.
>
>>
>> Something has been implemented but it needs/ed to be activated
>> by setting parameters (at least in June, didn't check later).
>>
>
> At present with default plugin=NULL, readRAST6() checks the list of drivers
> and if "GRASS" is present, and if the current and raster file regions agree,
> and only one raster is requested, it imports the raster directly into a
> SpatialGridDataFrame object using readGDAL(). If Rainer's data are in a
> raster that has the same region as the current region, the plugin would
> solve the problem.

No - the raster is covering a larger area, and the current region
covers only a small area of the raster.

>
> I can look at using r.out.gdal for making the temporary file, but IIRC, it
> suffers from the region mismatch problem that r.out.bin solves by resampling
> on the fly.
>
> Hope this helps,
>
> Roger
>
>
>
>> Markus
>>
>
>
>
>
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>



-- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
Biology, UCT), Dipl. Phys. (Germany)

Centre of Excellence for Invasion Biology
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University of Stellenbosch
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