installr (version 0.8)

ask.user.for.a.row: Asks the user for a row number from a data.frame table

Usage

ask.user.for.a.row(TABLE,
    header_text = "Possible versions to download (choose one)",
    questions_text = "Please review the table of versions from above, and enter the row number of the file-version you'd like to install: ")
TABLE{a data.frame table with rows from which we
  wish the user to choose a row.  If TABLE is not a
  data.frame, it will be coerced into one.}

  header_text{the text the users sees (often a
  question) as a title for the printed table - explaining
  which row he should choose from}

  questions_text{the question the users see after
  the printing of the table - explaining which row he
  should choose from}
The row number the user has choosen from the data.frame
  table.
The function gets a data.frame and asks the user to
  choose a row number.  Once choosen, that row number is
  returned from the function.
This function is used in installr when we are not
  sure what version of the software to download, or when
  various actions are available for the user to choose
  from. If the user doesn't give a valid row number, the
  function repeats its questions until a valid row number
  is chosen (or the user escapes)
version_table <- data.frame(versions = c("devel", "V 1.0.0", "V 2.0.0"))
installr:::ask.user.for.a.row(version_table)

source

On how to ask the user for input: http://stackoverflow.com/questions/5974967/what-is-the-correct-way-to-ask-for-user-input-in-an-r-program