| 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. 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.
Usage
match.arg(arg)
match.arg(arg, choices)
Arguments
arg |
a character string |
choices |
a character vector of candidate values |
Value
The unabbreviated version of the unique partial match if there is one; otherwise, an error is signalled.
See Also
pmatch
Examples
## 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
center(x, "m") # Error
## Actually, it would be nicer if one could catch the error
## to produce a more helpful error message ...