Suppose I have a function in my environment defined as follows:
abc <- function(x, a, b=23) { return(paste(x, a, b, sep=';')) }
I would like to get a reference to the above function by its name in the environment and be able to call it replacing its parameters. So an example:
> fun.abc <- get.fun.from.env('abc') #`fun.abc` should be the same as `abc` (above)
> x <- 123
> addl.params <- c(a=245, b=345)
> do.call(fun.abc, list(x, addl.params))
123;245;345
How would I implement this idea?
do.call will accept a function name as a string so:
fun.name <- "abc"
do.call(fun.name, c(x, as.list(addl.params)))
## [1] "123;245;345"
You may need to specify the envir= argument of do.call if fun.name is not in an environment reachable from the do.call.
*** UPDATE. After brief discussion with G. Grothendieck I see how to do it now:
> fun.abc <- get('abc')
> x <- 123
> addl.params <- c(a=245, b=345)
#somewhere else when I have a pointer to fun.abc
> do.call(fun.abc, c(x, as.list(addl.params)))
*** THIS WAS MY FIRST ATTEMPT AT THIS:
I came close to what I wanted to do in a somewhat different way. Hoping someone might be able to propose a way to achieve what I originally intended...
apply.fun <- function(func.id, x, ...) {
func.def <- load.func.spec.from.db(func.id)
def.args <- eval(str2lang(func.def$params))
args <- replace(def.args, names(...), as.list(...))
do.call(func.def$fun, list(x=x, unlist(args)))
}
get("abc")? Just curious: why can't you useabcas function instead offun.abc?