RQGIS (version 0.2.0)

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,
  show_msg = 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 to 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.

show_msg

Logical, if TRUE, Python messages that occured during the algorithm execution will be shown.

load_output

Character vector containing paths to (an) output file(s) in order 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 otherwise 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 the QGIS Python API through 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$INPUT <- random_points
# Here I specify a SpatialPointsDataFrame as input, but one could also
# specify the path to a spatial object file (e.g., shapefile), e.g.;
# params$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)
# }