RQGIS (version 0.1.0)

run_qgis: Interface to QGIS commands

Description

run_qgis calls QGIS algorithms from within R while passing the corresponding function arguments.

Usage

run_qgis(alg = NULL, params = NULL, check_params = TRUE, load_output = NULL, qgis_env = set_env())

Arguments

alg

Name of the GIS function to be used (see find_algorithms).

params

A list of geoalgorithm function arguments that should be used in conjunction with the selected (Q)GIS function (see get_args_man). Please make sure that you provide all function arguments in the correct order. To make sure this is the case, it is recommended to use the convenience function get_args_man.

check_params

If TRUE (default), it will be checked if all geoalgorithm function arguments were provided in the correct order.

load_output

Character vector containing paths to (an) output file(s) to load the QGIS output directly into R (optional). If load_output consists of more than one element, a list will be returned. See the example section for more details.

qgis_env

Environment containing all the paths to run the QGIS API. For more information, refer to set_env.

Value

If not otherwiese specified, the function saves the QGIS generated output files in a temporary folder. Optionally, function parameter load_output loads spatial QGIS output (vector and raster data) into R.

Details

This workhorse function calls QGIS via Python (QGIS API) using the command line. Specifically, it calls processing.runalg.

Examples

## Not run: 
# # set the environment
# my_env <- set_env()
# # find out how a function is called
# find_algorithms(search_term = "add", qgis_env = my_env)
# # specify parameters
# params <- get_args_man("saga:addcoordinatestopoints", qgis_env = my_env)
# # load random_points - a SpatialPointsDataFrame
# data(random_points, package = "RQGIS")
# params$INPUT <- random_points
# # Here I specify a SpatialPointsDataFrame as input, but you could also
# # specify the path to a spatial object file (e.g., shapefile), e.g.;
# # params$INPUT <- "random_points.shp"
# params$OUTPUT <- "output.shp"
# # Run the QGIS API and load its output into R
# run_qgis(alg = "saga:addcoordinatestopoints",
#          params = params,
#          load_output = params$OUTPUT,
#          qgis_env = my_env)
# ## End(Not run)