R: Attach or load packages, and automatically install missing...

pkg_attach {xfun} | R Documentation

## Attach or load packages, and automatically install missing packages if requested

### Description

`pkg_attach()` is a vectorized version of `library()` over the `package` argument to attach multiple packages in a single function call. `pkg_load()` is a vectorized version of `requireNamespace()` to load packages (without attaching them). The functions `pkg_attach2()` and `pkg_load2()` are wrappers of `pkg_attach(install = TRUE)` and `pkg_load(install = TRUE)`, respectively. `loadable()` is an abbreviation of `requireNamespace(quietly = TRUE)`. `pkg_available()` tests if a package with a minimal version is available.

### Usage

    pkg_attach(
      ...,
      install = FALSE,
      message = getOption("xfun.pkg_attach.message", TRUE)
    )

    pkg_load(..., error = TRUE, install = FALSE)

    loadable(pkg, strict = TRUE, new_session = FALSE)

    pkg_available(pkg, version = NULL)

    pkg_attach2(...)

    pkg_load2(...)

### Arguments

`...` | Package names (character vectors, and must always be quoted).
`install` | Whether to automatically install packages that are not available using `install.packages()`. Besides `TRUE` and `FALSE`, the value of this argument can also be a function to install packages (`install = TRUE` is equivalent to `install = install.packages`), or a character string `"pak"` (equivalent to `install = pak::pkg_install`, which requires the pak package). You are recommended to set a CRAN mirror in the global option `repos` via `options()` if you want to automatically install packages.
`message` | Whether to show the package startup messages (if any startup messages are provided in a package).
`error` | Whether to signal an error when certain packages cannot be loaded.
`pkg` | A single package name.
`strict` | If `TRUE`, use `requireNamespace()` to test if a package is loadable; otherwise only check if the package is in `.packages(TRUE)` (this does not really load the package, so it is less rigorous but on the other hand, it can keep the current R session clean).
`new_session` | Whether to test if a package is loadable in a new R session. Note that `new_session = TRUE` implies `strict = TRUE`.
`version` | A minimal version number. If `NULL`, only test if a package is available and do not check its version.

### Details

These are convenience functions that aim to solve these common problems: (1) We often need to attach or load multiple packages, and it is tedious to type several `library()` calls; (2) We are likely to want to install the packages when attaching/loading them but they have not been installed.

### Value

`pkg_attach()` returns `NULL` invisibly. `pkg_load()` returns a logical vector, indicating whether the packages can be loaded.

### See Also

`pkg_attach2()` is similar to `pacman::p_load()`, but does not allow non-standard evaluation (NSE) of the `...` argument, i.e., you must pass a real character vector of package names to it, and all names must be quoted. Allowing NSE adds too much complexity with too little gain (the only gain is that it saves your effort in typing two quotes).

### Examples

    library(xfun)
    pkg_attach("stats", "graphics")
    # pkg_attach2('servr') # automatically install servr if it is not installed

    (pkg_load("stats", "graphics"))

[Package xfun version 0.23 Index]