old.packages indicates packages which have a (suitable) later
  version on the repositories whereas update.packages offers to
  download and install such packages.
new.packages looks for (suitable) packages on the repositories
  that are not already installed, and optionally offers them for
  installation.
update.packages(lib.loc = NULL, repos = getOption("repos"),
                contriburl = contrib.url(repos, type),
                method, instlib = NULL,
                ask = TRUE, available = NULL,
                oldPkgs = NULL, …, checkBuilt = FALSE,
                type = getOption("pkgType"))old.packages(lib.loc = NULL, repos = getOption("repos"),
             contriburl = contrib.url(repos, type),
             instPkgs = installed.packages(lib.loc = lib.loc, …),
             method, available = NULL, checkBuilt = FALSE, …,
             type = getOption("pkgType"))
new.packages(lib.loc = NULL, repos = getOption("repos"),
             contriburl = contrib.url(repos, type),
             instPkgs = installed.packages(lib.loc = lib.loc, …),
             method, available = NULL, ask = FALSE, …,
             type = getOption("pkgType"))
character vector describing the location of R
    library trees to search through (and update packages therein), or
    NULL for all known trees (see .libPaths).
character vector, the base URL(s) of the repositories
    to use, e.g., the URL of a CRAN mirror such as
    "https://cloud.r-project.org".
URL(s) of the contrib sections of the
    repositories.  Use this argument if your repository is
    incomplete.  Overrides argument repos.
    Incompatible with type = "both".
Download method, see download.file.
    Unused if a non-NULL available is supplied.
character string giving the library directory where to install the packages.
logical indicating whether to ask the user to select
    packages before they are downloaded and installed, or the character
    string "graphics", which brings up a widget to allow the user
    to (de-)select from the list of packages which could be updated.
    (The latter value only works on systems with a GUI version of
    select.list, and is otherwise equivalent to
    ask = TRUE.)
an object as returned by available.packages
    listing packages available at the repositories, or NULL which
    makes an internal call to available.packages.
    Incompatible with type = "both".
If TRUE, a package built under an earlier
    major.minor version of R (e.g., 3.4) is considered to be
    ‘old’.
if specified as non-NULL, update.packages() only considers
    these packages for updating. This may be a character vector
    of package names or a matrix as returned by old.packages.
by default all installed packages,
    installed.packages(lib.loc = lib.loc).  A subset can be
    specified; currently this must be in the same (character matrix)
    format as returned by installed.packages().
Arguments such as destdir and dependencies to be
    passed to install.packages and
    ignore_repo_cache, max_repo_cache_age and
    noCache to available.packages or
    installed.packages.
character, indicating the type of package to download and
    install.  See install.packages.
update.packages returns NULL invisibly.
For old.packages, NULL or a matrix with one row per
  package, row names the package names and column names
  "Package", "LibPath", "Installed" (the version),
  "Built" (the version built under), "ReposVer" and
  "Repository".
For new.packages a character vector of package names,
  after any selected via ask have been installed.
Take care when using dependencies (passed to
  install.packages) with update.packages,
  for it is unclear where new dependencies should be installed.  The
  current implementation will only allow it if all the packages to be
  updated are in a single library, when that library will be used.
old.packages compares the information from
  available.packages with that from instPkgs (computed by
  installed.packages by default) and reports installed
  packages that have newer versions on the repositories or, if
  checkBuilt = TRUE, that were built under an earlier minor
  version of R (for example built under 3.3.x when running R 3.4.0).
  (For binary package types there is no check that the version on the
  repository was built under the current minor version of R,
  but it is advertised as being suitable for this version.)
new.packages does the same comparison but reports uninstalled
  packages that are available at the repositories.  If
  ask != FALSE it asks which packages should be installed in the
  first element of lib.loc.
The main function of the set is update.packages.  First a list
  of all packages found in lib.loc is created and compared with
  those available at the repositories.  If ask = TRUE (the
  default) packages with a newer version are reported and for each one
  the user can specify if it should be updated.  If so the packages are
  downloaded from the repositories and installed in the respective
  library path (or instlib if specified).
For how the list of suitable available packages is determined see
  available.packages.  available = NULL make a call
  to available.packages(contriburl = contriburl, method = method)
  and hence by default filters on R version, OS type and removes
  duplicates.
install.packages,
  available.packages, download.packages,
  installed.packages, contrib.url.
The options listed for install.packages under
  options.
See download.file for how to handle proxies and
  other options to monitor file transfers.
INSTALL, REMOVE, remove.packages,
  library, .packages, read.dcf
The ‘R Installation and Administration’ manual for how to set up a repository.