On Sat, 21 Nov 2009, Paul Hiemstra wrote:
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")
Maybe reading:
args(writeGDAL)
function (dataset, fname, drivername = "GTiff", type = "Float32",
mvFlag = NA, options = NULL, copy_drivername = "GTiff")
would help?
You are getting:
dataset=sp_hsm_pard, fname=out_pard, drivername="AAIGrid", type="Float32",
options="DECIMAL_PRECISION=3", mvFlag="NODATA=-9999"
by argument names and positions, I think, where internally
as.double("NODATA=-9999") is being coerced to an NA (a warning may have
been shown.
Perhaps try setting mvFlag=-9999? If you wanted to put it in the options,
that may work, but as.double(mvFlag) is explicitly set as the no-data
value on the band(s) being written in create2GDAL() inside writeGDAL().
Hope this helps,
Roger
--
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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--
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.biv...@nhh.no
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