Reputation: 618
Let's say I create a list using the assign
function:
name <- "test_list"
assign(name, list(a = c(1,2), b = c(3,4)))
Now, let's say I want to assign a new value to test_list
without typing it out directly (like in a situation where I want objects with specific names to be generated automatically).
Both of the following attempts didn't work:
1.)
as.name(name)$a[[1]] <- 5
2.)
eval(expr = as.name(name))$a[[1]] <- 5
Any ideas?
Upvotes: 1
Views: 621
Reputation: 887991
We can use
assign(name, `[<-`(get(name), get(name)$a[1], 5))
Or make this more explicit
assign(name, {dat <- get(name); dat$a[1] <- 5; dat})
Or extract the object from the globalenv and assign
.GlobalEnv[[name]]$a[1] <- 5
test_list
#$a
#[1] 5 2
#$b
#[1] 3 4
Upvotes: 2
Reputation: 24888
One approach is with eval(parse(text=expression))
, which can often be pressed into service in an emergency. But I would try to avoid it as much as possible.
name <- "test_list"
assign(name, list(a = c(1,2), b = c(3,4)))
eval(parse(text=paste0(name,"$a[[1]] <- 5")))
test_list
$a
[1] 5 2
$b
[1] 3 4
Upvotes: 1