match.arg {base}R Documentation

Argument Verification Using Partial Matching

Description

match.arg matches arg against a table of candidate values as specified by choices.

Usage

match.arg(arg, choices)

Arguments

arg a character string
choices a character vector of candidate values

Details

In the one-argument form match.arg(arg), the choices are obtained from a default setting for the formal argument arg of the function from which match.arg was called.

Matching is done using pmatch, so arg may be abbreviated.

Value

The unabbreviated version of the unique partial match if there is one; otherwise, an error is signalled.

See Also

pmatch, match.fun, match.call.

Examples

require(stats)
## Extends the example for 'switch'
center <- function(x, type = c("mean", "median", "trimmed")) {
  type <- match.arg(type)
  switch(type,
         mean = mean(x),
         median = median(x),
         trimmed = mean(x, trim = .1))
}
x <- rcauchy(10)
center(x, "t")       # Works
center(x, "med")     # Works
try(center(x, "m"))  # Error

[Package base version 2.1.0 Index]