[R] Obtaining variable's names from a list of variables

[Marc Schwartz]

On Aug 17, 2011, at 1:46 AM, Monsieur Do wrote:

> Say I have a list of variables, 
> 
> listVar <- list(age,sex)
> 
> I am looking for a way to either
> 
> 1- create a vector c("age","sex") from it, or
> 2- get the names one by one in a for loop such as these
> 
>     a)  for (i in 1:length(listVar)) rownames(result)[i] <- ???
> 
>     b)  for(i in listVar) print (variable's name)
> 
> 
> Any help much appreciated.

Based upon the way in which you created 'listVar', there really is not a way to recover the variable names, since they are not retained:

age <- 1:2
sex <- c("M", "F")
listVar <- list(age, sex)

> listVar
[[1]]
[1] 1 2

[[2]]
[1] "M" "F"

> names(listVar)
NULL


On the other hand, if you use:

listVar <- list(age = age, sex = sex)

> listVar
$age
[1] 1 2

$sex
[1] "M" "F"

> names(listVar)
[1] "age" "sex"

HTH,

Marc Schwartz