[GRASS-stats] "g.region: command not found" using readRAST6 command

[Roger Bivand]

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 <daniel.mcinerney at ucd.ie>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: Roger.Bivand at nhh.no