get name of an object inside a loop

Question

I know the deparse+substitute trick to get the name from an object passed as argument to a function, but the same trick inside a loop does no work.

My code (just for testing):

mylist <- list(first = c("lawyer","janitor"), second = c("engineer","housewife"))

for (element in names(mylist)){
  print(deparse(substitute(mylist[[element]])))
}

[1] "mylist[[element]]"
[1] "mylist[[element]]"

is there any way of getting the result?:

first
second

In your example you can just use print(element)..

talat
– talat

2017-02-14 08:59:27 +00:00
Commented Feb 14, 2017 at 8:59 — talat
– talat, Commented Feb 14, 2017 at 8:59
What's wrong with names(mylist) ?

Ronak Shah
– Ronak Shah

2017-02-14 08:59:50 +00:00
Commented Feb 14, 2017 at 8:59 — Ronak Shah
– Ronak Shah, Commented Feb 14, 2017 at 8:59

Sathish · Accepted Answer · 2017-02-14 09:04:52Z

2

using lapply

lapply(mylist, function(x) { print(names(x))} )
# NULL
# NULL
# $first
# NULL
# 
# $second
# NULL

using for loop as per your question

for (element in names(mylist)){
  print(element)
}
# [1] "first"
# [1] "second"

edited Feb 14, 2017 at 9:04

answered Feb 14, 2017 at 8:58

Sathish

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1 Comment

talat Over a year ago

The lapply is doing something slightly different, since it applies the names function to each list element, returning NULL because they don't have names in the example.

useRj · Accepted Answer · 2017-02-14 09:06:24Z

1

Use "names"

for (element in names(mylist)){
  print(as.name(element))
}

answered Feb 14, 2017 at 9:06

useRj

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