| switch {base} | R Documentation |
switch evaluates EXPR and accordingly chooses one of the
further arguments (in ...).
switch(EXPR, ...)
EXPR |
an expression evaluating to a number or a character string. |
... |
the list of alternatives, given explicitly. |
If the value of EXPR is an integer between 1 and
nargs()-1 then the corresponding element of ... is
evaluated and the result returned.
If EXPR returns a character string then that string is used to
match the names of the elements in .... If there is an exact
match then that element is evaluated and returned if there is one,
otherwise the next element is chosen, e.g.,
switch("cc", a=1, cc=, d=2) evaluates to 2.
In the case of no match, if there's a further argument in switch(..)
that one is returned, otherwise NULL.
centre <- function(x, type) {
switch(type,
mean = mean(x),
median = median(x),
trimmed = mean(x, trim = .1))
}
x <- rcauchy(10)
centre(x, "mean")
centre(x, "median")
centre(x, "trimmed")
ccc <- c("b","QQ","a","A","bb")
for(ch in ccc) cat(ch,":",switch(ch, a=1, b=2:3), "\n")
for(ch in ccc) cat(ch,":",switch(ch, a=,A=1, b=2:3, "Otherwise: last"),"\n")
## Numeric EXPR don't allow an `otherwise':
for(i in c(-1:3,9)) print(switch(i, 1,2,3,4))