Interact with the user to choose a CRAN mirror.
chooseCRANmirror(graphics = getOption("menu.graphics"), ind = NULL,
                 local.only = FALSE)getCRANmirrors(all = FALSE, local.only = FALSE)
Logical.  If true, use a graphical list: on Windows or
    the macOS GUI use a list box, and on a Unix-alike  use a Tk widget if
    package tcltk and an X server are available.  Otherwise use a
    text menu.
Optional numeric value giving which entry to select.
Logical, get all known mirrors or only the ones flagged as OK.
Logical, try to get most recent list from the CRAN master or use file on local disk only.
None for chooseCRANmirror(), this function is invoked for its
  side effect of updating options("repos").
getCRANmirrors() returns a data frame with mirror information.
A list of mirrors is stored in file
  R_HOME/doc/CRAN_mirrors.csv, but first an on-line
  list of current mirrors is consulted, and the file copy used only if
  the on-line list is inaccessible.
This function is called by a Windows GUI menu item and by
  contrib.url if it finds the initial dummy value of
  options("repos").
HTTPS mirrors with mirroring over ssh will be offered in
  preference to other mirrors (which are listed in a sub-menu).
ind chooses a row in the list of current mirrors, by number. It
  is best used with local.only = TRUE and row numbers in
   R_HOME/doc/CRAN_mirrors.csv.