deparse (base)

Expression Deparsing

Description

Turn unevaluated expressions into character strings.

Usage

deparse(expr, width.cutoff = 60,
        backtick = mode(expr) %in% c("call", "expression", "("),
        control = "showAttributes")

Arguments

expr any :R: expression.
width.cutoff

at which line-breaking is tried. |

backtick

enclosed in backticks if they do not follow the standard syntax. |

control

.deparseOpts. |

Details

This function turns unevaluated expressions (where “expression” is taken in a wider sense than the strict concept of a vector of mode “expression” used in expression) into character strings (a kind of inverse parse).

A typical use of this is to create informative labels for data sets and plots. The example shows a simple use of this facility. It uses the functions deparse and substitute to create labels for a plot which are character string versions of the actual arguments to the function myplot.

The default for the backtick option is not to quote single symbols but only composite expressions. This is a compromise to avoid breaking existing code.

Using control = “all” comes closest to making deparse() an inverse of parse(). However, not all objects are deparseable even with this option and a warning will be issued if the function recognizes that it is being asked to do the impossible.

Note

To avoid the risk of a source attribute out of sync with the actual function definition, the source attribute of a function will never be deparsed as an attribute.

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth \& Brooks/Cole.

See Also

substitute, parse, expression.

Quotes for quoting conventions, including backticks.

Examples

require(stats)
deparse(args(lm))
deparse(args(lm), width = 500)
myplot <-
function(x, y) {
    plot(x, y, xlab=deparse(substitute(x)),
        ylab=deparse(substitute(y)))
}
e <- quote(`foo bar`)
deparse(e)
deparse(e, backtick=TRUE)
e <- quote(`foo bar`+1)
deparse(e)
deparse(e, control = "all")

Wiki discussion

 
rdoc/base/deparse.txt · Last modified: 2006/06/12
 
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