R: apply list of functions on list of argument by name

Question

Someone has solved my question applying list of functions on list of argument by order, now I have another similar question, how to apply function in the list my name? For example, if I have:

f1 <- function(x) {x}
f2 <- function(x) {2*x}
f3 <- function(x) {3*x}
fun_list <- list(good=f1, better=f2, best=f3)
arg_list <- list(better=1, best=2, good=3)

I want to get the list of functions called on their respective named parameter, i.e., I want:

some_magic_fun(fun_list, arg_list) == list(f1(3), f2(1), f3(2)) 

What would be good way to do it?

Answer 1

As I understand it you want to choose the functions and the arguments from lists not necessarily in order but that have a common set of names:

 lapply(names(fun_list), function(n) fun_list[[n]](arg_list[[n]]) )
#----------
[[1]]
[1] 3

[[2]]
[1] 2

[[3]]
[1] 6

It wasn't entirely clear if you want the results but that was what I assumed. If you really wanted unevaluated expressions, you will need to clarify.

Answer 2

1) mapply This does not give a list (2 below does) but it may be what you really want:

> mapply(do.call, fun_list, lapply(arg_list[names(fun_list)], list))
good better   best 
   3      2      6 

2) Map This gives a list as the result which is what was asked for. Its the same as (1) except mapply is replaced with Map:

> Map(do.call, fun_list, lapply(arg_list[names(fun_list)], list))
$good
[1] 3

$better
[1] 2

$best
[1] 6

Revised based on comments.