rgrass7 (version 0.2-10)

initGRASS: Initiate GRASS session

Description

Run GRASS interface in an R session not started within GRASS. In general, most users will use initGRASS in throwaway locations, to use GRASS modules on R objects without the need to define and populate a location. The function initializes environment variables used by GRASS, the .gisrc used by GRASS for further environment variables, and a temporary location.

On Windows, if OSGeo4W GRASS is being used, the R session must be started in the OSGeo4W shell. If not, the non-standard placing of files and of environment variables confuses the function. If toupper(gisBase) contains “OSGEO4W64/APPS/GRASS” or “OSGEO4W/APPS/GRASS” (and after converting “\” to “/”), but the environment variable OSGEO4W_ROOT is not defined, initGRASS() will exit with an error before confusion leads to further errors. For further details, see https://github.com/rsbivand/rgrass/issues/16 and https://lists.osgeo.org/pipermail/grass-stats/2018-November/001800.html.

The locking functions are used internally, but are exposed for experienced R/GRASS scripters needing to use the GRASS module “g.mapset” through initGRASS in an existing GRASS location. In particular, “g.mapset” may leave a .gislock file in the current MAPSET, so it may be important to call unlink_.gislock to clean up before quitting the R session. remove_GISRC may be used to try to remove the file given in the “GISRC” environment variable if created by initGRASS with argument remove_GISRC= TRUE.

Usage

initGRASS(gisBase, home, SG, gisDbase, addon_base, location, mapset,
  override = FALSE, use_g.dirseps.exe = TRUE, pid, remove_GISRC=FALSE,
  ignore.stderr=get.ignore.stderrOption())
get.GIS_LOCK()
set.GIS_LOCK(pid)
unset.GIS_LOCK()
unlink_.gislock()
remove_GISRC()

Value

The function runs gmeta6 before returning the current values of the running GRASS session that it provides.

Arguments

gisBase

The directory path to GRASS binaries and libraries, containing bin and lib subdirectories among others

home

The directory in which to create the .gisrc file; defaults to $HOME on Unix systems and to USERPROFILE on Windows systems; can usually be set to tempdir()

SG

An optional SpatialGrid object to define the DEFAULT_WIND of the temporary location; if use_sp() has not been called, it will be called internally if SG is given as an object inheriting from "Spatial"; if use_sf() has been called, it will be overridden internally as only objects inheriting from "Spatial" may be given.

gisDbase

if missing, tempdir() will be used; GRASS GISDBASE directory for the working session

addon_base

if missing, assumed to be “$HOME/.grass7/addons” on Unix-like platforms, on MS Windows “%APPDATA%\GRASS7\addons”, and checked for existence

location

if missing, basename(tempfile()) will be used; GRASS location directory for the working session

mapset

if missing, basename(tempfile()) will be used; GRASS mapset directory for the working session

override

default FALSE, set to TRUE if accidental trashing of GRASS .gisrc files and locations is not a problem

use_g.dirseps.exe

default TRUE; when TRUE appears to work for WinGRASS Native binaries, when FALSE for QGIS GRASS binaries; ignored on other platforms.

pid

default as.integer(round(runif(1, 1, 1000))), integer used to identify GIS_LOCK; the value here is arbitrary, but probably should be set correctly

remove_GISRC

default FALSE; if TRUE, attempt to unlink the temporary file named in the “GISRC” environment variable when the R session terminates or when this package is unloaded

ignore.stderr

default taking the value set by set.ignore.stderrOption; can be set to TRUE to silence system() output to standard error; does not apply on Windows platforms

Author

Roger S. Bivand, e-mail:

Details

The function establishes an out-of-GRASS working environment providing GRASS commands with the environment variable support required, and may also provide a temporary location for use until the end of the running R session if the home argument is set to tempdir(), and the gisDbase argument is not given. Running gmeta6 shows where the location is, should it be desired to archive it before leaving R.

See Also

gmeta

Examples

GRASS_INSTALLATION <- Sys.getenv("GRASS_INSTALLATION")
run <- FALSE
if (nzchar(GRASS_INSTALLATION)) run <- file.info(GRASS_INSTALLATION)$isdir
run <- run && require(terra, quietly=TRUE)
if (run) {
f <- system.file("ex/elev.tif", package="terra")
r <- rast(f)
plot(r, col=grDevices::terrain.colors(50))
}
if (run) {
(loc <- initGRASS(GRASS_INSTALLATION, home=tempdir(), SG=r, override=TRUE))
}
if (run) {
write_RAST(r, "elev", flags="overwrite")
execGRASS("r.info", map="elev")
}
if (run) {
s <- rast(r)
values(s) <- values(r)
write_RAST(s, "elev1", flags="overwrite")
execGRASS("r.info", map="elev1")
}
if (run) {
execGRASS("r.slope.aspect", flags="overwrite", elevation="elev", slope="slope", aspect="aspect")
}
if (run) {
u1 <- read_RAST(c("elev", "slope", "aspect"), return_format="terra")
plot(u1[["elev"]], col=grDevices::terrain.colors(50))
}