[R-sig-Geo] Writing an ASCII grid with nodata values

[Paul Hiemstra]

Hi Ned,

Is it an option to switch to another GDAL format, GTiff for example? 
Check if this exports the NA values correctly. Not really an answer to 
your question, but maybe a helpful suggestion.

cheers and good luck,
Paul

Ned Horning wrote:
> I am trying to export a SpatialPixelsDataFrame object with floating 
> point values to an ASCII grid file and want to specify a nodata value. 
> I tried write.asciigrid from the sp package and I couldn't figure out 
> how to output float values. The pixel values exported as integers.
>
> For now I am using the following writeGDAL statement:
> -- 
> writeGDAL(sp_hsm_pard, out_pard, drivername="AAIGrid", type="Float32", 
> options="DECIMAL_PRECISION=3", "NODATA=-9999")
>
> -- 
> This appears to output the image okay but it is not assigning the 
> proper values to NODATA_value. The NODATA_value in the exported file 
> is "1" instead of "-9999".
>
> Can someone let me know how to output floating point data to an ESRI 
> ASCII grid file and specify a nodata value.
>
> Thanks,
>
> Ned
>
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-- 
Drs. Paul Hiemstra
Department of Physical Geography
Faculty of Geosciences
University of Utrecht
Heidelberglaan 2
P.O. Box 80.115
3508 TC Utrecht
Phone:  +3130 274 3113 Mon-Tue
Phone:  +3130 253 5773 Wed-Fri
http://intamap.geo.uu.nl/~paul