RQGIS (version 1.0.4)

get_extent: Retrieve the joint extent of all specified spatial objects

Description

Retrieve the joint extent of all specified spatial objects by running through a parameter-argument list while merging the extents of all spatial objects. This is mostly needed for the GRASS_REGION_PARAMETER. Still there are geoalgorithms which require an extent object.

Usage

get_extent(params, type_name)

Arguments

params

A parameter-argument list as returned by get_args_man() or pass_args(), which contains all spatial objects from which the joint extent should be retrieved.

type_name

A character string containing the QGIS parameter type for each parameter (boolean, multipleinput, extent, number, etc.) of params. The Python method RQGIS.get_args_man returns a Python dictionary with one of its elements corresponding to the type_name (see also the example section).

Examples

# NOT RUN {
library("RQGIS")
library("raster")
library("reticulate")
r <- raster(ncol = 100, nrow = 100)
r1 <- crop(r, extent(-10, 11, -10, 11))
r2 <- crop(r, extent(0, 20, 0, 20))
r3 <- crop(r, extent(9, 30, 9, 30))
r1[] <- 1:ncell(r1)
r2[] <- 1:ncell(r2)
r3[] <- 1:ncell(r3)
alg <- "grass7:r.patch"
out <- py_run_string(sprintf("out = RQGIS.get_args_man('%s')", alg))$out
params <- get_args_man(alg)
params$input <- list(r1, r2, r3)
get_extent(params = params, type_name = out$type_name)
# or if we save the input rasters in files stored on disk
params[] <- save_spatial_objects(params = params,
                                 type_name = out$type_name)
get_extent(params = params, type_name = out$type_name)
# }