Creating unique object names for list entries

August 15, 2022

I have example data as follows:

listoflists=
    list( 
        list(a = c(1,'a',3,4) , b = c(5,'b',6,7) ), 
        list(a = c(1,'a',2,6) , b = c(5,'b',0,8) ), 
        list(d = c(1,'a',2,6) , b = c(5,'b',0,8) ),
        list(d = c(1,'a',2,3) , b = c(5,'b',0,8) , a = c(5,'b',0,8)),
        list(d = c(1,'a',1,1))
    )

I would like rename the names (such as a and b), (only) if they have already been used. For example by adding a number at the end.

I am having some trouble thinking of the right way to approach this..

Any suggestions?

>Solution :

Maybe there is a more elegant way but just going through the list and renaming items while keeping count of each name’s uses works fine:

# all used names
names.used <- unique(unlist(sapply(listoflists, names)))
# usage counter for each name
names.n <- setNames(rep(0, length(names.used)), names.used)

for (i in seq_along(listoflists)) {
  for (j in seq_along(listoflists[[i]])) {
    
    name.ij <- names(listoflists[[i]])[j]
    
    # rename second and further occurrences
    if (names.n[name.ij] > 0) {
      names(listoflists[[i]])[j] <- paste0(name.ij, names.n[name.ij])
    }
    
    # update counter
    names.n[name.ij] <- names.n[name.ij] + 1
  }
}

# [[1]]
# [[1]]$a
# [1] "1" "a" "3" "4"
# 
# [[1]]$b
# [1] "5" "b" "6" "7"
# 
# 
# [[2]]
# [[2]]$a1
# [1] "1" "a" "2" "6"
# 
# [[2]]$b1
# [1] "5" "b" "0" "8"
# 
# 
# [[3]]
# [[3]]$d
# [1] "1" "a" "2" "6"
# 
# [[3]]$b2
# [1] "5" "b" "0" "8"
# 
# 
# [[4]]
# [[4]]$d1
# [1] "1" "a" "2" "3"
# 
# [[4]]$b3
# [1] "5" "b" "0" "8"
# 
# [[4]]$a2
# [1] "5" "b" "0" "8"
# 
# 
# [[5]]
# [[5]]$d2
# [1] "1" "a" "1" "1"