On Wed, 7 Oct 2009, Tim Holland wrote:
Hi Daniel,
No, as it was I was trying to run things through R. Grass was (is) running,
but just incidentally. Your comment made me think I needed to run
initGRASS() first, so I tried, but got the following:
initGRASS(gisBase="/Library/GRASS/6.4",
gisDbase="/Users/timholland/Documents/GIS/Vietnam_General/VN_GrassDbase")
Error in initGRASS(gisBase = "/Library/GRASS/6.4", gisDbase =
"/Users/timholland/Documents/GIS/Vietnam_General/VN_GrassDbase") :
A GISRC file already exists; to override, set override=TRUE
Should I be running R through GRASS? (as opposed to vice-versa, as had been
my understanding). If so, how do I do that?
Whether you run spgrass6 freestanding or within a running GRASS depends on
what you want to do. If you only need to use GRASS analytical modules
(programs) on data that are "on the R side", the freestanding possibility
may be sufficient, as initGRASS() essentially sets up the GRASS
environment variables for you and creates a throw-away location in a
temporary directory. Then you can use write*6() to populate it, and work
from there, probably bringing the results back with read*6().
If on the other hand you have (or ought to have) a GRASS location and wish
to analyse the data in R (other way round), you start R within a running
GRASS shell, so that it inherits the environment variables and existing
location.
Beware of the GRASS/GDAL plugin - if you get odd things happening with
readRAST6(), use the plugin=FALSE argument, as this will read your data
using a temporary file instead. If you are not using the plugin, setting
the mapset should not be needed. In addition, your mapset path looks
highly non-standard - mapsets are typically within the GISDBASE and
LOCATION in a hierarchy.
When you get non-obvious error messages, please do include the output of
traceback() run immediately after the error. This permits the
identification of where in the call tree (sequence of functions called by
the function you used) the problem arose. The output of sessionInfo() is
also potentially useful.
Hope this clarifies a little.
Roger
Again, sorry for really basic questions, but thank you for the help.
Best,
Tim
On Wed, Oct 7, 2009 at 3:52 PM, Daniel McInerney <[email protected]>wrote:
Hi Tim,
Is R running within a GRASS session?
Regards,
Daniel.
Tim Holland wrote:
Hello,
I'm sorry to keep making so much noise on the list for what I'm sure are
basic questions.
I am having trouble loading in a GRASS raster into R using the readRAST6
command.
Using:
readRAST6("rasterMap",mapset="/Users/etc/my_mapset")
I get the following error:
Error in if (file.exists(file) == FALSE) if (!missing(asText) && asText
==
: argument is of length zero
Error in parseGRASS(cmd) : g.region not parsed
sh: g.region: command not found
Is there something I am doing wrong here?
Also, when I am working with spgrass6 in general, should I have my working
directory set to the GRASS DBase I am using, or does that matter?
Thank you for the help, Tim
sessionInfo()
R version 2.9.2 (2009-08-24) i386-apple-darwin8.11.1
locale:
en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] spgrass6_0.6-9 XML_2.6-0 rgdal_0.6-12 sp_0.9-44
loaded via a namespace (and not attached):
[1] grid_2.9.2 lattice_0.17-25
--
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: [email protected]
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