Convert vector like c(“x”,“y”,“z”) to function(x , y, z){}

Question

How to convert vector like c("x","y","z") to function(x , y, z){} in R?

I am looking for something like reverse function of formalArgs() .

Note that, I know about as.function(alist(x=,y=,{})) but I don't know how to insert x= and y= in it from a given vector.

Answer 1

Basically to get this to work you need to call

as.function(alist(x=, y=, z=, {}))`

which is equivalent to

as.function(alist(x=bquote(), y=bquote(), z=bquote(), {}))

The second form is nice because we have a set of named arguments to alist , which can provide programmatically using a list and do.call :

l <- list(x=bquote(), y=bquote(), z=bquote(), bquote({}))
as.function(do.call(alist, l))
# function (x, y, z) 
# {
# }

All that remains is to construct our list l programmatically from the list of variable names, which can be done with setNames and replicate :

vec <- c("x","y","z")
as.function(do.call(alist, c(setNames(replicate(length(vec), bquote(), F), vec),
                             bquote({}))))
# function (x, y, z) 
# {
# }

Answer 2

The arguments are just a named list. The coercion to the internal pairlist is automatic.

#argument list
p<-c("x","y","z")
args<-vector("list",length(p))
for(i in seq(args)) args[[i]]<-substitute()
names(args)<-p

#set a default value for y for the sake of example
args$y<-2

#construct function
body<-quote(x+y+z)
f<-as.function(c(args,body))

#test it
f(1,z=3)
#[1] 6