| deparse {base} | R Documentation |
Expression Deparsing
Description
Turn unevaluated expressions into character strings.
Usage
deparse(expr, width.cutoff = 60L,
backtick = mode(expr) %in% c("call", "expression", "(", "function"),
control = c("keepNA", "keepInteger", "niceNames", "showAttributes"),
nlines = -1L)
deparse1(expr, collapse = " ", width.cutoff = 500L, ...)
Arguments
expr |
any R expression. |
width.cutoff |
integer in |
backtick |
logical indicating whether symbolic names should be enclosed in backticks if they do not follow the standard syntax. |
control |
character vector (or |
nlines |
integer: the maximum number of lines to produce. Negative values indicate no limit. |
collapse |
a string, passed to |
... |
further arguments passed to |
Details
These functions turn unevaluated expressions (where ‘expression’
is taken in a wider sense than the strict concept of a vector of
mode and type (typeof)
"expression" used in expression) into character
strings (a kind of inverse to 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.
width.cutoff is a lower bound for the line lengths: deparsing a
line proceeds until at least width.cutoff bytes have
been output and e.g. arg = value expressions will not be split
across lines.
deparse1() is a simple utility added in R 4.0.0 to ensure a
string result (character vector of length one),
typically used in name construction, as
deparse1(substitute(.)).
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.
Deparsing internal structures may not be accurate: for example the
graphics display list recorded by recordPlot is not
intended to be deparsed and .Internal calls will be shown as
primitive calls.
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
See Also
.deparseOpts for available control settings;
dput() and dump() for related functions using
identical internal deparsing functionality.
substitute,
parse,
expression.
Quotes for quoting conventions, including backticks.
Examples
require(stats); require(graphics)
deparse(args(lm))
deparse(args(lm), width.cutoff = 500)
myplot <- function(x, y) {
plot(x, y, xlab = deparse1(substitute(x)),
ylab = deparse1(substitute(y)))
}
e <- quote(`foo bar`)
deparse(e)
deparse(e, backtick = TRUE)
e <- quote(`foo bar`+1)
deparse(e)
deparse(e, control = "all") # wraps it w/ quote( . )