geotargets

geotargets extends targets to work with geospatial data formats, such as rasters and vectors (e.g., shapefiles).

A relatively common gotcha moment when using popular libraries like terra with targets is running into erros 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 this is for you :)

Installation

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"))

A note on development

geotargets is still undergoing development, and 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.

Examples

Below we show three examples of target factories:

• tar_terra_rast()
• tar_terra_vect()
• tar_terra_sprc()

You would use these in place of tar_target() in your targets pipeline, when you are doing work with terra raster or terra vector data.

It is a bit tricky to implement targets workflows in a README, but if you would like to see and download working examples for yourself, see the repo, demo-geotargets.

tar_terra_rast(): targets with terra rasters

library(targets)
tar_dir({ # tar_dir() runs code from a temporary directory.
  tar_script({
    library(targets)
    library(geotargets)
    list(
      tar_terra_rast(
        terra_rast_example,
        system.file("ex/elev.tif", package = "terra") |> terra::rast()
      )
    )
  })
  tar_make()
  x <- tar_read(terra_rast_example)
  x
})

tar_terra_vect(): targets with terra vectors

tar_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
})

tar_terra_sprc(): targets with terra raster collections

targets::tar_dir({ # tar_dir() runs code from a temporary directory.
  library(geotargets)
  targets::tar_script({
    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 good homolosine
        command = terra::sprc(list(
          elev_scale(1),
          elev_scale(2, "+proj=igh")
        ))
      )
    )
  })
  targets::tar_make()
  x <- targets::tar_read(raster_elevs)
})

Code of Conduct

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.