Question

I have apparently a simple one that my grey matter currently refuses to grasp – say I have a list:

list(a = "foo", b = c("bar", "biz", "booze"))

and a function fn. How can I get a string like this:

"fn(a = \"foo\", b = c(\"bar\", \"biz\", \"booze\"))"

P.S.

I know I’ll regret for asking this one in the morning…

Answer 1

You could also manipulate the language objects directly, as described in Chapter 6 of the R Language Definition:

X <- quote(list(a = "foo", b = c("bar", "biz", "booze")))
X[[1]] <- quote(fn)  ## as.symbol("fn") would also work
deparse(X)
# [1] "fn(a = \"foo\", b = c(\"bar\", \"biz\", \"booze\"))"

Or, if your list is already stored in a named object, you can just use c() and as.call() to piece together the desired call:

ll <- list(a = "foo", b = c("bar", "biz", "booze"))
deparse(as.call(c(as.symbol("fn"), ll)))
# [1] "fn(a = \"foo\", b = c(\"bar\", \"biz\", \"booze\"))"