spgrass6: execGRASS: make the output of the command an R object.

Hi

In older version of the execGRASS function of spgrass6, setting the option
intern=TRUE would make the output of the grass command a R object.

Now, when I run execGRASS with the intern=TRUE, like the statement below,
the output is not written to the R object.

a <- execGRASS("r.univar", flags="g", map=distmod, separator=";",
intern=TRUE)

The object 'a' is created, but it is empty (character(0)). However, when I
set legacyExec=TRUE (like below), the object 'a' is created with the grass
r.univar output.

a <- execGRASS("r.univar", flags="g", map=distmod, separator=";",
legacyExec=TRUE, intern=TRUE)

Is this the intended behaviour (i.e., did I miss something in the help
file)?

I am running R version 3.0.1 (2013-05-16), on Ubuntu 13.04 64-bit

Paulo

	[[alternative HTML version deleted]]

Great, this is really helpful. You are right, and I should have seen from
the help file, that the semicolon is not one of the supported separators.
The odd thing is it works when running r.univar from grass directly if I
use the table flag (-t instead of -g). But now I know I shouldn't.

Thanks for helping out, much appreciated!

Paulo





On Mon, May 20, 2013 at 7:38 PM, Roger Bivand <Roger.Bivand at nhh.no> wrote:

On Mon, 20 May 2013, Paulo van Breugel wrote:

 Hi

In older version of the execGRASS function of spgrass6, setting the option
intern=TRUE would make the output of the grass command a R object.

Now, when I run execGRASS with the intern=TRUE, like the statement below,
the output is not written to the R object.

a <- execGRASS("r.univar", flags="g", map=distmod, separator=";",
intern=TRUE)

With GRASS 6.4.2:

a <- execGRASS("r.univar", flags = "g", map = "elevation.dem", intern =
TRUE)

works as before. Adding the fs= parameter causes the failure. You are
using GRASS 7, in which fs= is separator=. In:

raster/r.univar/r.univar_main.**c

only \\t, tab, space, and comma are defined as such, others seem to be
accepted, but ";" is not. I think that the parameter is unused anyway in
script-style output, but setting fs=";" certainly causes trouble.

Try without that parameter. Your observed difference in behaviour is not
intended from the R side, and is caused by odd behaviour and interaction
between parameters on the GRASS side in this GRASS module for your
parameter settings. Other GRASS modules, and r.univar with different fs=
settings, work as expected on Unix platforms, but under Windows, legacy
execution is enforced anyway.

Hope this clarifies,

Roger

The object 'a' is created, but it is empty (character(0)). However, when I
set legacyExec=TRUE (like below), the object 'a' is created with the grass
r.univar output.

a <- execGRASS("r.univar", flags="g", map=distmod, separator=";",
legacyExec=TRUE, intern=TRUE)

Is this the intended behaviour (i.e., did I miss something in the help
file)?

I am running R version 3.0.1 (2013-05-16), on Ubuntu 13.04 64-bit

Paulo

        [[alternative HTML version deleted]]

--
Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
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

On Mon, 20 May 2013, Paulo van Breugel wrote:

Great, this is really helpful. You are right, and I should have seen from
the help file, that the semicolon is not one of the supported separators.
The odd thing is it works when running r.univar from grass directly if I
use the table flag (-t instead of -g). But now I know I shouldn't.

With GRASS 7:

a <- execGRASS("r.univar", flags = "t", map = "elevation.dem",
 separator="; ", intern = TRUE)

works, but:

a <- execGRASS("r.univar", flags = "t", map = "elevation.dem",
  separator=";", intern = TRUE)

does not. The problem is that the trailing ";" on the command line to
GRASS is also the shell line terminator, so must be protected by
quoting:

a <- execGRASS("r.univar", flags = "t", map = "elevation.dem",
  separator="';'", intern = TRUE)

or:

a <- execGRASS("r.univar", flags = "t", map = "elevation.dem",
separator=shQuote(";"), intern = TRUE)

both work.

Roger

Thanks for helping out, much appreciated!

Paulo





On Mon, May 20, 2013 at 7:38 PM, Roger Bivand <Roger.Bivand at nhh.no> wrote:

On Mon, 20 May 2013, Paulo van Breugel wrote:

 Hi

In older version of the execGRASS function of spgrass6, setting the option
intern=TRUE would make the output of the grass command a R object.

Now, when I run execGRASS with the intern=TRUE, like the statement below,
the output is not written to the R object.

a <- execGRASS("r.univar", flags="g", map=distmod, separator=";",
intern=TRUE)

With GRASS 6.4.2:

a <- execGRASS("r.univar", flags = "g", map = "elevation.dem", intern =
TRUE)

works as before. Adding the fs= parameter causes the failure. You are
using GRASS 7, in which fs= is separator=. In:

raster/r.univar/r.univar_main.**c

only \\t, tab, space, and comma are defined as such, others seem to be
accepted, but ";" is not. I think that the parameter is unused anyway in
script-style output, but setting fs=";" certainly causes trouble.

Try without that parameter. Your observed difference in behaviour is not
intended from the R side, and is caused by odd behaviour and interaction
between parameters on the GRASS side in this GRASS module for your
parameter settings. Other GRASS modules, and r.univar with different fs=
settings, work as expected on Unix platforms, but under Windows, legacy
execution is enforced anyway.

Hope this clarifies,

Roger

The object 'a' is created, but it is empty (character(0)). However, when I
set legacyExec=TRUE (like below), the object 'a' is created with the grass
r.univar output.

a <- execGRASS("r.univar", flags="g", map=distmod, separator=";",
legacyExec=TRUE, intern=TRUE)

Is this the intended behaviour (i.e., did I miss something in the help
file)?

I am running R version 3.0.1 (2013-05-16), on Ubuntu 13.04 64-bit

Paulo

        [[alternative HTML version deleted]]

--
Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
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