geotargets extends targets to
work with geospatial data formats, such as rasters and vectors (e.g.,
shapefiles). Currently we support raster and vector formats for the
terra package
You can install the development version of geotargets like so:
install.packages("geotargets", repos = c("https://njtierney.r-universe.dev", "https://cran.r-project.org"))If you want to use geospatial data formats (such as terra) with the
targets package to build
analytic reproducible pipelines, it involves writing a lot of custom
targets wrappers. We wrote geotargets so you can use geospatial data
formats with targets.
To provide more detail on this, a common problem when using popular
libraries like terra with targets is running into errors with read
and write. Due to the limitations that come with the underlying C++
implementation in the terra library, there are specific ways to write
and read these objects. See ?terra for details. geotargets helps
handle these write and read steps, so you don’t have to worry about them
and can use targets as you are used to.
In essence, if you’ve ever come across the error:
Error in .External(list(name = "CppMethod__invoke_notvoid", address = <pointer: 0x0>, :
NULL value passed as symbol address
or
Error: external pointer is not valid
When trying to read in a geospatial raster or vector in targets, then
geotargets for you :)
We currently provide support for the terra package with targets.
Below we show three examples of target factories:
tar_terra_rast()tar_terra_vect()tar_terra_sprc()tar_stars()
You would use these in place of tar_target() in your targets pipeline,
when you are doing work with terra raster, vector, or raster
collection data.
If you would like to see and download working examples for yourself, see the repo, demo-geotargets.
library(targets)
tar_dir({ # tar_dir() runs code from a temporary directory.
tar_script({
library(geotargets)
get_elev <- function() {
terra::rast(system.file("ex", "elev.tif", package = "terra"))
}
list(
tar_terra_rast(
terra_rast_example,
get_elev()
)
)
})
tar_make()
x <- tar_read(terra_rast_example)
x
})
#> ▶ dispatched target terra_rast_example
#> ● completed target terra_rast_example [0.019 seconds]
#> ▶ ended pipeline [0.185 seconds]
#> class : SpatRaster
#> dimensions : 90, 95, 1 (nrow, ncol, nlyr)
#> resolution : 0.008333333, 0.008333333 (x, y)
#> extent : 5.741667, 6.533333, 49.44167, 50.19167 (xmin, xmax, ymin, ymax)
#> coord. ref. : lon/lat WGS 84 (EPSG:4326)
#> source : terra_rast_example
#> name : elevation
#> min value : 141
#> max value : 547tar_dir({ # tar_dir() runs code from a temporary directory.
tar_script({
library(geotargets)
lux_area <- function(projection = "EPSG:4326") {
terra::project(terra::vect(system.file("ex", "lux.shp",
package = "terra")),
projection)
}
list(
tar_terra_vect(
terra_vect_example,
lux_area()
)
)
})
tar_make()
x <- tar_read(terra_vect_example)
x
})
#> ▶ dispatched target terra_vect_example
#> ● completed target terra_vect_example [0.034 seconds]
#> ▶ ended pipeline [0.173 seconds]
#> class : SpatVector
#> geometry : polygons
#> dimensions : 12, 6 (geometries, attributes)
#> extent : 5.74414, 6.528252, 49.44781, 50.18162 (xmin, xmax, ymin, ymax)
#> source : terra_vect_example
#> coord. ref. : lon/lat WGS 84 (EPSG:4326)
#> names : ID_1 NAME_1 ID_2 NAME_2 AREA POP
#> type : <num> <chr> <num> <chr> <num> <int>
#> values : 1 Diekirch 1 Clervaux 312 18081
#> 1 Diekirch 2 Diekirch 218 32543
#> 1 Diekirch 3 Redange 259 18664tar_dir({ # tar_dir() runs code from a temporary directory.
tar_script({
library(geotargets)
elev_scale <- function(z = 1, projection = "EPSG:4326") {
terra::project(
terra::rast(system.file("ex", "elev.tif", package = "terra")) * z,
projection
)
}
list(
tar_terra_sprc(
raster_elevs,
# two rasters, one unaltered, one scaled by factor of 2 and
# reprojected to interrupted goode homolosine
command = terra::sprc(list(
elev_scale(1),
elev_scale(2, "+proj=igh")
))
)
)
})
tar_make()
x <- tar_read(raster_elevs)
x
})
#> ▶ dispatched target raster_elevs
#> ● completed target raster_elevs [0.112 seconds]
#> ▶ ended pipeline [0.266 seconds]
#> Warning message:
#> [rast] skipped sub-datasets (see 'describe(sds=TRUE)'):
#> /private/var/folders/wr/by_lst2d2fngf67mknmgf4340000gn/T/Rtmpr9sjXA/targets_1085a12a40d0c/_targets/scratch/raster_elevs
#> class : SpatRasterCollection
#> length : 2
#> nrow : 90, 115
#> ncol : 95, 114
#> nlyr : 1, 1
#> extent : 5.741667, 1558890, 49.44167, 5556741 (xmin, xmax, ymin, ymax)
#> crs (first) : lon/lat WGS 84 (EPSG:4326)
#> names : raster_elevs, raster_elevstar_dir({ # tar_dir() runs code from a temporary directory.
tar_script({
library(geotargets)
list(
tar_stars(
test_stars,
stars::read_stars(system.file("tif", "olinda_dem_utm25s.tif", package = "stars"))
)
)
})
tar_make()
x <- tar_read(test_stars)
x
})
#> ▶ dispatched target test_stars
#> ● completed target test_stars [0.053 seconds]
#> ▶ ended pipeline [0.17 seconds]
#> Warning message:
#> In CPL_write_gdal(mat, file, driver, options, type, dims, from, :
#> GDAL Message 6: creation option '' is not formatted with the key=value format
#> stars object with 2 dimensions and 1 attribute
#> attribute(s):
#> Min. 1st Qu. Median Mean 3rd Qu. Max.
#> test_stars -1 6 12 21.66521 35 88
#> dimension(s):
#> from to offset delta refsys point x/y
#> x 1 111 288776 89.99 UTM Zone 25, Southern Hem... FALSE [x]
#> y 1 111 9120761 -89.99 UTM Zone 25, Southern Hem... FALSE [y]Please note that the geotargets project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.
geotargets is still undergoing development. We currently consider the
extensions with terra maturing and approaching stability. We would
love for people to use the package to kick the tyres. We are using it in
our own work, but want users to know that the API could change in subtle
or breaking ways.