qgisprocess
The goal of qgisprocess is to provide an R interface to the popular and open source desktop geographic information system (GIS) program QGIS. The package is a re-implementation of functionality provided by the archived RQGIS package, which was partially revived in the RQGIS3 package.
Installation
qgisprocess
You can install the development version from GitHub with:
# install.packages("remotes")
remotes::install_github("r-spatial/qgisprocess")QGIS
The qgisprocess package wraps the standalone qgis_process
command-line
utility,
which is available in QGIS >= 3.16.
The package is meant to support current QGIS releases, i.e. both the latest and the long-term release. Although older QGIS releases are not officially supported, it may work since QGIS 3.16. Download instructions for all platforms are available at https://download.qgis.org/.
If a recent version of QGIS isn’t available for your OS, you can use the
Geocomputation with R Docker
image with
QGIS installed (docker pull ghcr.io/geocompx/docker:qgis). See the
vignette on ‘getting started’ for more information.
Package configuration
If the automatic configuration fails (or if you have more than one
installation and would like to choose which one is used by
qgisprocess), you can set
options(qgisprocess.path = "path/to/qgis_process"). Specify the
qgisprocess.path option in your .Rprofile, to make your choices
persistent between sessions. You can run qgis_configure() to
reconfigure, or just qgis_configure(use_cached_data = TRUE) to see the
gritty details!
library(qgisprocess)
#> Attempting to load the cache ... Success!
#> QGIS version: 3.30.2-'s-Hertogenbosch
#> Having access to 1949 algorithms from 13 QGIS processing providers.
#> Run `qgis_configure(use_cached_data = TRUE)` to reload cache and get more details.Functionality
Most functions start with the qgis_ prefix, so that functions can be
found more easily using tab completion.
The main function is qgis_run_algorithm(algorithm = , ...). It
specifies the geoprocessing algorithm to be called with a
"provider:algorithm" formatted identifier, e.g. "native:convexhull"
or "gdal:hillshade", and it passes the algorithm arguments as R
function arguments.
Additional functions are provided to discover available geoprocessing algorithms, retrieve their documentation, handle processing results, manage QGIS plugins, and more.
Spatial layers can be passed to qgis_run_algorithm() as file paths but
also as sf,
stars,
terra or
raster objects.
A structured overview of functions is available at https://r-spatial.github.io/qgisprocess/reference/index.html. To get started, read the ‘getting started’ vignette and use the cheat sheets!
Note that R package qgis extends on qgisprocess by providing a separate R function for each geoprocessing algorithm. In addition, it makes the QGIS algorithm documentation available in the corresponding R function documentation.
Example
The following example demonstrates the buffer algorithm in action.
input <- sf::read_sf(system.file("shape/nc.shp", package = "sf"))
result <- qgis_run_algorithm(
"native:buffer",
INPUT = input,
DISTANCE = 1,
DISSOLVE = TRUE
)
#> Argument `SEGMENTS` is unspecified (using QGIS default value).
#> Using `END_CAP_STYLE = "Round"`
#> Using `JOIN_STYLE = "Round"`
#> Argument `MITER_LIMIT` is unspecified (using QGIS default value).
#> Using `OUTPUT = qgis_tmp_vector()`
result
#> <Result of `qgis_run_algorithm("native:buffer", ...)`>
#> List of 1
#> $ OUTPUT: 'qgis_outputVector' chr "/tmp/RtmpsCZuzJ/file7d1b75a4d4eb/file7d1b1ab3935f.gpkg"
output_sf <- sf::st_as_sf(result)
plot(sf::st_geometry(output_sf))
You can read the help associated with an algorithm using
qgis_show_help().
qgis_show_help("native:buffer")It may also be useful to run an algorithm in the QGIS GUI and examine the console ‘Input parameters’ to determine how the various input values are translated to string processing arguments:
A list of available algorithms can be found using qgis_algorithms().
When using R interactively, it may be useful to use
View(qgis_algorithms()) to search.
qgis_algorithms()
#> # A tibble: 1,949 × 24
#> provider provider_title algorithm algorithm_id algorithm_title
#> <chr> <chr> <chr> <chr> <chr>
#> 1 3d QGIS (3D) 3d:tessellate tessellate Tessellate
#> 2 cartographytools Cartography tools cartographyt… averagelines Average linest…
#> 3 cartographytools Cartography tools cartographyt… collapsedua… Collapse dual …
#> 4 cartographytools Cartography tools cartographyt… removecross… Remove cross r…
#> 5 cartographytools Cartography tools cartographyt… removeculde… Remove cul-de-…
#> 6 cartographytools Cartography tools cartographyt… removeround… Remove roundab…
#> 7 gdal GDAL gdal:aspect aspect Aspect
#> 8 gdal GDAL gdal:assignp… assignproje… Assign project…
#> 9 gdal GDAL gdal:bufferv… buffervecto… Buffer vectors
#> 10 gdal GDAL gdal:buildvi… buildvirtua… Build virtual …
#> # ℹ 1,939 more rows
#> # ℹ 19 more variables: provider_can_be_activated <lgl>,
#> # provider_is_active <lgl>, provider_long_name <chr>, provider_version <chr>,
#> # provider_warning <chr>, can_cancel <lgl>, deprecated <lgl>, group <chr>,
#> # has_known_issues <lgl>, help_url <chr>, requires_matching_crs <lgl>,
#> # short_description <chr>, tags <list>, default_raster_file_extension <chr>,
#> # default_vector_file_extension <chr>, …Further reading
- A paper on the original RQGIS package published in the R Journal
- A discussion options for running QGIS from R that led to this package
- The pull request in the
QGIS repo that led to the development of the
qgis_processcommand-line utility