Load the values of targets.

Load the return values of targets into the current environment (or the environment of your choosing). For a typical target, the return value lives in a file in _targets/objects/. For dynamic files (i.e. format = "file") the paths loaded in place of the values. tar_load_everything() is shorthand for tar_load(everything()) to load all targets.

Usage

tar_load(
  names,
  branches = NULL,
  meta = tar_meta(targets_only = TRUE, store = store),
  strict = TRUE,
  silent = FALSE,
  envir = parent.frame(),
  store = targets::tar_config_get("store")
)

Arguments

names

Names of the targets to load. You may supply tidyselect helpers like any_of() and starts_with(). Names are selected from the metadata in _targets/meta, which may include errored targets.

branches

Integer of indices of the branches to load for any targets that are patterns.

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.

strict

Logical of length 1, whether to error out if one of the selected targets is in the metadata but cannot be loaded. Set to FALSE to just load the targets in the metadata that can be loaded and skip the others.

silent

Logical of length 1. Only relevant when strict is FALSE. If silent is FALSE and strict is FALSE, then a message will be printed if a target is in the metadata but cannot be loaded. However, load failures will not stop other targets from being loaded.

envir

Environment to put the loaded targets.

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

Nothing.

Storage access

Several functions like tar_make(), tar_read(), tar_load(), tar_meta(), and tar_progress() read or modify the local data store of the pipeline. The local data store is in flux while a pipeline is running, and depending on how distributed computing or cloud computing is set up, not all targets can even reach it. So please do not call these functions from inside a target as part of a running pipeline. The only exception is literate programming target factories in the tarchetypes package such as tar_render() and tar_quarto().

Several functions like tar_make(), tar_read(), tar_load(), tar_meta(), and tar_progress() read or modify the local data store of the pipeline. The local data store is in flux while a pipeline is running, and depending on how distributed computing or cloud computing is set up, not all targets can even reach it. So please do not call these functions from inside a target as part of a running pipeline. The only exception is literate programming target factories in the tarchetypes package such as tar_render() and tar_quarto().

See also

Other data: tar_crew(), tar_load_everything(), tar_load_raw(), tar_objects(), tar_pid(), tar_process(), tar_read_raw(), tar_read()

Examples

if (identical(Sys.getenv("TAR_EXAMPLES"), "true")) { # for CRAN
tar_dir({ # tar_dir() runs code from a temp dir for CRAN.
tar_script({
  list(
    tar_target(y1, 1 + 1),
    tar_target(y2, 1 + 1),
    tar_target(z, y1 + y2)
  )
}, ask = FALSE)
tar_make()
ls() # Does not have "y1", "y2", or "z".
tar_load(starts_with("y"))
ls() # Has "y1" and "y2" but not "z".
tar_load(any_of("z"))
ls() # Has "y1", "y2", and "z".
})
}