options                 package:base                 R Documentation

Options Settings

Description:

     `options' allows the user to set and examine a variety of global
     ``options'' which affect the way in which R computes and displays
     its results.

Usage:

     options(...)
     getOption(x)
     .Options

Arguments:

     ...: any options can be defined, using `name = value'.

          However, only the ones below are used in ``base R''.

          Further, `options('name') == options()['name']', see the
          example. 

  prompt: a string, used for R's prompt; should usually end in a blank
          (`" "').

continue: a string setting the prompt used for lines which continue
          over one line.

   width: controls the number of characters on a line.  You may want to
          change this if you re-size the window that R is running in.
          Valid values are 10...10000 with default normally 80. (The
          valid values are in file `Print.h' and can be changed by
          re-compiling R.)

  digits: controls the number of digits to print when printing numeric
          values.  It is a suggestion only.  Valid values are 1...22
          with default 7.

  editor: sets the default text editor, e.g., for `edit'.  Set from the
          environment variable `VISUAL' on UNIX.

   pager: the (stand-alone) program used for displaying ASCII files on
          R's console. Defaults to `$R_HOME/bin/pager'. 

 browser: default HTML browser used by `help.start()' on UNIX.

  mailer: default mailer used by `bug.report()'. can be `"none"'.

contrasts: the default `contrasts' used in model fitting such as with
          `aov' or `lm'.  A character vector of length two, the first
          giving the function to be used with unordered factors and the
          second the function to be used with ordered factors.

expressions: sets a limit on the number of nested expressions that will
          be evaluated.  This is especially important on the Macintosh
          since stack overflow is likely if this is set too high. Valid
          values are 25...100000 with default 500.

keep.source: When `TRUE', the source code for functions (newly defined
          or loaded) is stored in their `"source"' attribute (see
          `attr') allowing comments to be kept in the right places.

          The default is `interactive()', i.e., `TRUE' for interactive
          use.

keep.source.pkgs: As for `keep.source', for functions in packages
          loaded by `library' or `require'. Defaults to `FALSE' unless
          the environment variable `R_KEEP_PKG_SOURCE' is set to `yes'.

na.action: the name of a function for treating missing values (`NA''s)
          for certain situations.

papersize: the default paper format used by `postscript'; set by
          environment variable `R_PAPERSIZE' when R is started and
          defaulting to `"a4"' if that is unset or invalid.

printcmd: the command used by `postscript' for printing; set by
          environment variable `R_PRINTCMD' when R is started. This
          should be a command that expects either input to be piped to
          `stdin' or to be given a single filename argument. 

latexcmd, dvipscmd: character strings giving commands to be used in
          off-line printing of help pages.

show.signif.stars, show.coef.Pvalues: logical, affecting P value
          printing, see `print.coefmat'.

  ts.eps: the relative tolerance for certain time series (`ts')
          computations.

   error: either a function or an expression governing the handling of
          non-catastrophic errors such as those generated by `stop' as
          well as by signals and internally detected errors.  If the
          option is a function, a call to that function, with no
          arguments, is generated as the expression.  The default value
          is `NULL': see `stop' for the behaviour in that case. The
          function `dump.frames' provides one alternative that allows
          post-mortem debugging.

show.error.messages: a logical. Should error messages be printed? 
          Intended for use with `try' or a user-installed error
          handler.

    warn: sets the handling of warning messages.  If `warn' is negative
          all warnings are ignored.  If `warn' is zero (the default)
          warnings are stored until the top-level function returns.  If
          fewer than 10 warnings were signalled they will be printed
          otherwise a message saying how many (max 50) were signalled. 
          A top-level variable called `last.warning' is created and can
          be viewed through the function `warnings'.  If `warn' is one,
          warnings are printed as they occur.  If `warn' is two or
          larger all warnings are turned into errors.

check.bounds: logical, defaulting to `FALSE'.  If true, a warning is
          produced whenever a ``generalized vector'' (atomic or `list')
          is extended, by something like `x <- 1:3; x[5] <- 6'.

    echo: logical.  Only used in non-interactive mode, when it controls
          whether input is echoed. Command-line option `--slave' sets
          this initially to `FALSE'.

 verbose: logical.  Should R report extra information on progress? Set
          to `TRUE' by the command-line option `--verbose'.

  device: a character string giving the default device for that
          session. This defaults to the normal screen device (e.g.
          `x11', `windows' or `gtk') for an interactive session, and
          `postscript' in batch use or if a screen is not available.

X11colortype: The default colour type for `X11' devices.

    CRAN: The URL of the preferred CRAN node for use by
          `update.packages'. Defaults to <URL:
          http://cran.r-project.org>.

download.file.method: Method to be used for `download.file'. Currently
          download methods `"internal"', `"wget"' and `"lynx"' are
          available.  There is no default for this option, when `method
          = "auto"' is chosen: see `download.file'.

   unzip: the command used unzipping help files. 

de.cellwidth: integer: the cell widths (number of  characters) to be
          used in the data editor `dataentry'.  If this is unset, 0,
          negative or `NA', variable cell widths are used.

encoding: An integer vector of length 256 holding an input encoding. 
          Defaults to `native.enc' (= `0:255'). See `connections'.

 timeout: Integer.  The timeout for Internet operations, in seconds. 
          Default 60 seconds.

internet.info: The minimum level of information to be printed on url
          downloads etc. Default is 2, for failure causes.  Set to 1 or
          0 to get more information.

       x: a character string holding one of the above option names.

Details:

     Invoking `options()' with no arguments returns a list with the
     current values of the options.  To access the value of a single
     option, one should use `getOption("width")', e.g., rather than
     `options("width")' which is a list of length one.

     `.Options' also always contains the `options()' list, for S
     compatibility.  You must use it ``read only'' however.

     The default settings of some of these options are

       `prompt'             `"> "'     `continue'           `"+ "'
       `width'              `80'       `digits'             `7'
       `expressions'        `500'      `keep.source'        `TRUE'
       `show.signif.stars'  `TRUE'     `show.coef.Pvalues'  `TRUE'
       `na.action'          `na.omit'  `ts.eps'             `1e-5'
       `error'              `NULL'     `warn'               `0'
       `echo'               `TRUE'     `verbose'            `FALSE'

     Others are set from environment variables or are
     platform-dependent.

Value:

     A list (in any case) with the previous values of the options
     changed, or all options when no arguments were given.

Examples:

     options() # printing all current options
     op <- options(); str(op) # nicer printing

     # .Options is the same:
     all(sapply(1:length(op), function(i) all(.Options[[i]] == op[[i]])))

     options('width')[[1]] == options()$width # the latter needs more memory
     options(digits=20)
     pi

     # set the editor, and save previous value
     old.o <- options(editor="nedit")
     old.o

     options(check.bounds = TRUE)
     x <- NULL; x[4] <- "yes" # gives a warning

     options(op)     # reset (all) initial options
     options('digits')

     ## set contrast handling to be like S
     options(contrasts=c("contr.helmert", "contr.poly"))

     ## on error, terminate the R session with error status 66
     options(error=quote(q("no", status=66, runLast=FALSE)))
     stop("test it")

     ## set an error action for debugging: see ?debugger.
     options(error=quote(dump.frames()))
     ## A possible setting for non-interactive sessions
     options(error=quote({dump.frames(to.file=TRUE); q()}))

