[GRASS-stats] How to use r.what in rgrass7?

[Rainer M Krug]

Markus Neteler <neteler at osgeo.org> writes:

> Dear list,
>
> I try to query from R a raster map at given vector point positions
> (both maps are in GRASS but it could well be that the points are in R
> and the (huge) raster map in GRASS).
>
> So, simple North Carolina data set example:
>
> goutput <- execGRASS("r.what", map="elev_state_500m",
> points="geodetic_pts", separator=",")

Which data set do you mean? I don't have the maps in the
nc_basic_spm_grass7 dataset?

did you try to use intern=TRUE :

,----
| intern: default NULL, in which case set internally from
|           ‘get.useInternOption’; a logical (not 'NA') which indicates
|           whether to make the output of the command an R object. Not
|           available unless 'popen' is supported on the platform
`----

Other options to try:

,----
| Sys_ignore.stdout, Sys_wait, Sys_input: pass extra arguments to
|           ‘system’
| 
| Sys_show.output.on.console, Sys_minimized, Sys_invisible: pass extra
|           arguments to ‘system’ on Windows systems only
`----

Cheers,

Rainer

>
> I would expect that the result is stored in "goutput" (seems it is)
> but it also dumps it into the terminal which I would like to avoid. I
> don't manage to switch that off.
>
> Then, following this blog
> https://pvanb.wordpress.com/2013/01/23/import-grass-function-console-output-as-data-frame-in-r/
>
> I tried to parse the output:
> con <- textConnection(goutput)
>
> which fails with
> Error in textConnection(goutput) : invalid 'text' argument
>
> Does anyone have a suggestion how to turn the output of r.what into an R object?
>
> Likewise suggestions are welcome how to feed R point positions into
> r.what from R.
>
> Hope I am not asking too much :-)
>
> thanks,
> Markus
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-- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology, UCT), Dipl. Phys. (Germany)

Centre of Excellence for Invasion Biology
Stellenbosch University
South Africa

Tel :       +33 - (0)9 53 10 27 44
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email:      Rainer at krugs.de

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