set_env: Retrieve the environment settings to run QGIS from within R
In RQGIS: Integrating R with QGIS

Description Usage Arguments Value Author(s) Examples

set_env tries to find all the paths necessary to run QGIS from within R.

1	set_env(root = NULL, new = FALSE, dev = FALSE, ...)

`root`	Root path to the QGIS-installation. If left empty, the function looks for `qgis.bat` first in the most likely locations (C:/OSGEO4~1, C:/OSGEO4~2), and secondly on the C: drive under Windows. On a Mac, it looks for `QGIS.app` under "Applications" and "/usr/local/Cellar/". On Linux, `set_env` assumes that the root path is "/usr".
`new`	When called for the first time in an R session, `set_env` caches its output. Setting `new` to `TRUE` resets the cache when calling `set_env` again. Otherwise, the cached output will be loaded back into R even if you used new values for function arguments `root` and/or `dev`.
`dev`	If set to `TRUE`, `set_env` will use the development version of QGIS (if available). Since RQGIS so far does not support QGIS 3 (developer version), setting `dev` to TRUE will result in an error message under Windows.
`...`	Currently not in use.

The function returns a list containing all the path necessary to run QGIS from within R. This is the root path, the QGIS prefix path and the path to the Python plugins.

Jannes Muenchow, Patrick Schratz

## Not run: 
# Letting set_env look for the QGIS installation might take a while depending
# on how full the C: drive is (Windows)
set_env()
# It is much faster (0 sec) to explicitly state the root path to the QGIS
# installation
set_env("C:/OSGEO4~1")  # Windows example

## End(Not run)