options {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.
`digits` | controls the number of digits to print when printing numeric values. It is a suggestion only.
`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.
`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` | an expression governing the handling of non-catastrophic errors such as those generated by `stop` as well as by signals and internally detected errors. The default expression 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.

`echo` | logical. Only used in non-interactive mode, when it controls whether input is echoed. Command-line options `--quiet` and `--slave` set 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 http://cran.r-project.org.
`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.
`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.

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(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()}))

[Package Contents]