[GRASS-stats] readRAST6() issue with NODATA

[Roger Bivand]

On Sat, 12 Jun 2010, Markus Neteler wrote:

> Dear Roger,
>
> hope all is well.
>
> I came across an issue with readRAST6():
>
>> library(spgrass6)
> Loading required package: sp
> Loading required package: rgdal
> Geospatial Data Abstraction Library extensions to R successfully loaded
> Loaded GDAL runtime: GDAL 1.5.2, released 2008/05/29
> Path to GDAL shared files: /home/neteler/binaries/share/gdal
> Loaded PROJ.4 runtime: Rel. 4.6.1, 21 August 2008
> Path to PROJ.4 shared files: (autodetected)
> Loading required package: XML
> GRASS GIS interface loaded with GRASS version: 6.4.0svn
> and location: patUTM32
>> mydata_raw <-readRAST6(c("thresh_annual_over_11_celsius_2001_2008_avg", "italy_dem20_PHD_zone"), cat=c(FALSE, FALSE))
> /home/neteler/grassdata/patUTM32/zanzara_satellite/.tmp/fep/thresh_annual_over_11_celsius_2001_2008_avg
> has GDAL driver GTiff
> and has 601 rows and 1011 columns
> WARNING: The given nodata value is present in rasterband
>         <italy_dem20_PHD_zone> and would lead to data loss. Please specify
>         a different nodata value with the nodata parameter.
> ERROR: Raster export aborted.
>
> Debugging r.out.gdal, I found that the value 10 was used.
>
>
> GRASS 6.4.0svn (patUTM32): > r.info -r italy_dem20_PHD_zone
> min=0
> max=3890
> GRASS 6.4.0svn (patUTM32): > r.info -t italy_dem20_PHD_zone
> datatype=CELL
>
> I hacked in -99999 as NODATA value in the r.out.gdal calls
> (spgrass6/R/bin_link.R).
>
> I have no idea why 10 was used but from GRASS 6.4 onwards the r.out.gdal
> module has an intelligent NODATA selection thanks to Markus Metz. I can
> imagine what you don't want to clutter the code with conditions, but here it
> would be great to let the NODATA selection job to r.out.gdal rather than
> using the current r.info tricks.

Dear Markus,

The tricks were there for the time when r.out.gdal didn't find its own 
value, and for the null parameter for r.out.bin. I've moved them down to 
the r.out.bin branch only, and modified the execGRASS() call to r.out.gdal 
to omit the nodata= argument by default when NODATA=NULL.

Committed to sourceforge CVS, project r-spatial, module spgrass6. Could 
you check this and let me know if the problem is resolved?

Best wishes,

Roger

>
> What do you think?
>
> Best,
> Markus
>
> PS: off for 2 weeks now
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>

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no