targets: tar_read – R documentation

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tar_read

Read a target's value from storage.

Description

Read a target's return value from its file in _targets/objects/. For dynamic files (i.e. format = "file") the paths are returned.

Usage

tar_read(
  name,
  branches = NULL,
  meta = tar_meta(store = store),
  store = targets::tar_config_get("store")
)

Arguments

`name`	Symbol, name of the target to read.
`branches`	Integer of indices of the branches to load if the target is a pattern.
`meta`	Data frame of metadata from `tar_meta()`. `tar_read()` with the default arguments can be inefficient for large pipelines because all the metadata is stored in a single file. However, if you call `tar_meta()` beforehand and supply it to the `meta` argument, then successive calls to `tar_read()` may run much faster.
`store`	Character of length 1, path to the `targets` data store. Defaults to `tar_config_get("store")`, which in turn defaults to `_targets/`. When you set this argument, the value of `tar_config_get("store")` is temporarily changed for the current function call. See `tar_config_get()` and `tar_config_set()` for details about how to set the data store path persistently for a project.

Value

The target's return value from its file in _targets/objects/, or the paths to the custom files and directories if format = "file" was set.

Limited scope

tar_read() and tar_load() are only for exploratory analysis and literate programming, and tar_read_raw() and tar_load_raw() are only for exploratory analysis. targets automatically loads the correct dependencies into memory when the pipeline is running, so invoking these functions from inside a target is rarely advisable.

Examples

if (identical(Sys.getenv("TAR_EXAMPLES"), "true")) {
tar_dir({ # tar_dir() runs code from a temporary directory.
tar_script(list(tar_target(x, 1 + 1)), ask = FALSE)
tar_make()
tar_read(x)
})
}

targets

Dynamic Function-Oriented 'Make'-Like Declarative Workflows

v0.10.0

MIT + file LICENSE

Authors

William Michael Landau [aut, cre] (<https://orcid.org/0000-0003-1878-3253>), Matthew T. Warkentin [ctb], Samantha Oliver [rev] (<https://orcid.org/0000-0001-5668-1165>), Tristan Mahr [rev] (<https://orcid.org/0000-0002-8890-5116>), Eli Lilly and Company [cph]

Initial release