That won't work because R has special rules for evaluating things in the
function position. Examples:
*OK*
min(1:2)
"min"(1:2)
f<-min; f(1:2)
do.call(min,list(1:2))
do.call("min",list(1:2)) # do.call converts string->function
*Not OK*
("min")(1:2) # string in function position is not converted
f<-"min"; f(1:2) # ditto
f<- c("min","max"); f[1](1:2) # ditto
What you need to do is make 'f' a list of *function values, *not a vector
of strings:
f<- c(min,max)
and then select the element of f with [[ ]] (select one element), not [ ]
(select sublist):
f[[1]](1:2)
Thus your example becomes
type <- c(min,max)
n <- 1:10
for (a in 1:2) {
print(type[[a]](n)) }
Another (uglier) approach is with do.call:
type <- c("min","max")
n <- 1:10
for (a in 1:2) {
print(do.call(type[a],list(n))) }
Does that help?
-s
On Tue, Feb 14, 2012 at 14:02, Muhammad Rahiz
<muhammad.ra...@ouce.ox.ac.uk>wrote:
> Hi all,
>
> I'm trying to get the min and max of a sequence of number using a loop
> like the folllowing. Can anyone point me to why it doesn't work.
>
> Thanks.
>
> type <- c("min","max")
> n <- 1:10
> for (a in 1:2) {
> print(type[a](n)) }
>
>
> --
> Muhammad
>
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