tar_terra_sprc: Create a terra _SpatRasterCollection_ target

In geotargets: 'targets' Extensions for Geographic Spatial Formats

Create a terra SpatRasterCollection target

Description

Provides a target format for terra::SpatRasterCollection objects, which have no restriction in the extent or other geometric parameters.

Usage

tar_terra_sprc(
  name,
  command,
  pattern = NULL,
  filetype = geotargets_option_get("gdal.raster.driver"),
  gdal = geotargets_option_get("gdal.raster.creation.options"),
  ...,
  tidy_eval = targets::tar_option_get("tidy_eval"),
  packages = targets::tar_option_get("packages"),
  library = targets::tar_option_get("library"),
  repository = targets::tar_option_get("repository"),
  error = targets::tar_option_get("error"),
  memory = targets::tar_option_get("memory"),
  garbage_collection = targets::tar_option_get("garbage_collection"),
  deployment = targets::tar_option_get("deployment"),
  priority = targets::tar_option_get("priority"),
  resources = targets::tar_option_get("resources"),
  storage = targets::tar_option_get("storage"),
  retrieval = targets::tar_option_get("retrieval"),
  cue = targets::tar_option_get("cue"),
  description = targets::tar_option_get("description")
)

Arguments

name	Symbol, name of the target. A target name must be a valid name for a symbol in R, and it must not start with a dot. See targets::tar_target() for more information.
command	R code to run the target.
pattern	Code to define a dynamic branching pattern for a target. See targets::tar_target() for more information.
filetype	character. File format expressed as GDAL driver names passed to terra::writeRaster().
gdal	character. GDAL driver specific datasource creation options. passed to terra::writeRaster()
...	Additional arguments not yet used.
tidy_eval	Logical, whether to enable tidy evaluation when interpreting command and pattern. If TRUE, you can use the "bang-bang" operator ⁠!!⁠ to programmatically insert the values of global objects.
packages	Character vector of packages to load right before the target runs or the output data is reloaded for downstream targets. Use tar_option_set() to set packages globally for all subsequent targets you define.
library	Character vector of library paths to try when loading packages.
repository	Character of length 1, remote repository for target storage. Choices: "local": file system of the local machine. "aws": Amazon Web Services (AWS) S3 bucket. Can be configured with a non-AWS S3 bucket using the endpoint argument of tar_resources_aws(), but versioning capabilities may be lost in doing so. See the cloud storage section of https://books.ropensci.org/targets/data.html for details for instructions. "gcp": Google Cloud Platform storage bucket. See the cloud storage section of https://books.ropensci.org/targets/data.html for details for instructions. A character string from tar_repository_cas() for content-addressable storage. Note: if repository is not "local" and format is "file" then the target should create a single output file. That output file is uploaded to the cloud and tracked for changes where it exists in the cloud. The local file is deleted after the target runs.
error	Character of length 1, what to do if the target stops and throws an error. Options: "stop": the whole pipeline stops and throws an error. "continue": the whole pipeline keeps going. "null": The errored target continues and returns NULL. The data hash is deliberately wrong so the target is not up to date for the next run of the pipeline. In addition, as of targets version 1.8.0.9011, a value of NULL is given to upstream dependencies with error = "null" if loading fails. "abridge": any currently running targets keep running, but no new targets launch after that. "trim": all currently running targets stay running. A queued target is allowed to start if: It is not downstream of the error, and It is not a sibling branch from the same tar_target() call (if the error happened in a dynamic branch). The idea is to avoid starting any new work that the immediate error impacts. error = "trim" is just like error = "abridge", but it allows potentially healthy regions of the dependency graph to begin running. (Visit https://books.ropensci.org/targets/debugging.html to learn how to debug targets using saved workspaces.)
memory	Character of length 1, memory strategy. Possible values: "auto" (default): equivalent to memory = "transient" in almost all cases. But to avoid superfluous reads from disk, memory = "auto" is equivalent to memory = "persistent" for for non-dynamically-branched targets that other targets dynamically branch over. For example: if your pipeline has tar_target(name = y, command = x, pattern = map(x)), then tar_target(name = x, command = f(), memory = "auto") will use persistent memory in order to avoid rereading all of x for every branch of y. "transient": the target gets unloaded after every new target completes. Either way, the target gets automatically loaded into memory whenever another target needs the value. "persistent": the target stays in memory until the end of the pipeline (unless storage is "worker", in which case targets unloads the value from memory right after storing it in order to avoid sending copious data over a network). For cloud-based file targets (e.g. format = "file" with repository = "aws"), the memory option applies to the temporary local copy of the file: "persistent" means it remains until the end of the pipeline and is then deleted, and "transient" means it gets deleted as soon as possible. The former conserves bandwidth, and the latter conserves local storage.
garbage_collection	Logical: TRUE to run base::gc() just before the target runs, in whatever R process it is about to run (which could be a parallel worker). FALSE to omit garbage collection. Numeric values get converted to FALSE. The garbage_collection option in tar_option_set() is independent of the argument of the same name in tar_target().
deployment	Character of length 1. If deployment is "main", then the target will run on the central controlling R process. Otherwise, if deployment is "worker" and you set up the pipeline with distributed/parallel computing, then the target runs on a parallel worker. For more on distributed/parallel computing in targets, please visit https://books.ropensci.org/targets/crew.html.
priority	Deprecated on 2025-04-08 (targets version 1.10.1.9013). targets has moved to a more efficient scheduling algorithm (https://github.com/ropensci/targets/issues/1458) which cannot support priorities. The priority argument of tar_target() no longer has a reliable effect on execution order.
resources	Object returned by tar_resources() with optional settings for high-performance computing functionality, alternative data storage formats, and other optional capabilities of targets. See tar_resources() for details.
storage	Character string to control when the output of the target is saved to storage. Only relevant when using targets with parallel workers (https://books.ropensci.org/targets/crew.html). Must be one of the following values: "worker" (default): the worker saves/uploads the value. "main": the target's return value is sent back to the host machine and saved/uploaded locally. "none": targets makes no attempt to save the result of the target to storage in the location where targets expects it to be. Saving to storage is the responsibility of the user. Use with caution.
retrieval	Character string to control when the current target loads its dependencies into memory before running. (Here, a "dependency" is another target upstream that the current one depends on.) Only relevant when using targets with parallel workers (https://books.ropensci.org/targets/crew.html). Must be one of the following values: "auto" (default): equivalent to retrieval = "worker" in almost all cases. But to avoid unnecessary reads from disk, retrieval = "auto" is equivalent to retrieval = "main" for dynamic branches that branch over non-dynamic targets. For example: if your pipeline has tar_target(x, command = f()), then tar_target(y, command = x, pattern = map(x), retrieval = "auto") will use "main" retrieval in order to avoid rereading all of x for every branch of y. "worker": the worker loads the target's dependencies. "main": the target's dependencies are loaded on the host machine and sent to the worker before the target runs. "none": targets makes no attempt to load its dependencies. With retrieval = "none", loading dependencies is the responsibility of the user. Use with caution.
cue	An optional object from tar_cue() to customize the rules that decide whether the target is up to date.
description	Character of length 1, a custom free-form human-readable text description of the target. Descriptions appear as target labels in functions like tar_manifest() and tar_visnetwork(), and they let you select subsets of targets for the names argument of functions like tar_make(). For example, tar_manifest(names = tar_described_as(starts_with("survival model"))) lists all the targets whose descriptions start with the character string "survival model".

Details

The terra package uses objects like terra::SpatRaster, terra::SpatVector, and terra::SpatRasterDataset (SDS), which do not contain the data directly–they contain a C++ pointer to memory where the data is stored. As a result, these objects are not portable between R sessions without special handling, which causes problems when including them in targets pipelines with targets::tar_target(). The functions, tar_terra_rast(), tar_terra_sds(), tar_terra_sprc(), tar_terra_tiles(), and tar_terra_vect() handle this issue by writing and reading the target as a geospatial file (specified by filetype) rather than saving the relevant object (e.g., SpatRaster, SpatVector, etc.), itself.

Value

target class "tar_stem" for use in a target pipeline

Note

The iteration argument is unavailable because it is hard-coded to "list", the only option that works currently.

Author(s)

Andrew Gene Brown

Nicholas Tierney

See Also

targets::tar_target_raw()

Examples

# For CRAN. Ensures these examples run under certain conditions.
# To run this locally, run the code inside this if statement
if (Sys.getenv("TAR_LONG_EXAMPLES") == "true") {
  targets::tar_dir({ # tar_dir() runs code from a temporary directory.
    targets::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 good homolosine
          command = terra::sprc(list(
            elev_scale(1),
            elev_scale(2, "+proj=igh")
          ))
        )
      )
    })
    targets::tar_make()
    targets::tar_read(raster_elevs)
  })
}

geotargets documentation built on June 8, 2025, 11:54 a.m.