Convert Mixed-Length named List to data.frame

Question

I have a list of the following format:

[[1]]
[[1]]$a
[1] 1

[[1]]$b
[1] 3

[[1]]$c
[1] 5

[[2]]       
[[2]]$c
[1] 2

[[2]]$a
[1] 3

There i

Answer 1

If you know the possible values beforehand, and you are dealing with large data, perhaps using data.table and set will be fast

cc <- createList(50000)



system.time({
nas <- rep.int(NA_real_, length(cc))
DT <-  setnames(as.data.table(replicate(length(ids),nas, simplify = FALSE)), ids)

for(xx in seq_along(cc)){

  .n <- names(cc[[xx]])
  for(j in .n){
    set(DT, i = xx, j = j, value = cc[[xx]][[j]])
  }


}

})


# user  system elapsed 
# 0.68    0.01    0.70 

---

Old (slow solution) for posterity

full <- c('a','b', 'c')

system.time({
for(xx in seq_along(cc)) {
  mm <- setdiff(full, names(cc[[xx]]))
  if(length(mm) || all(names(cc[[xx]]) == full)){
  cc[[xx]] <- as.data.table(cc[[xx]])
  # any missing columns

  if(length(mm)){
  # if required add additional columns
    cc[[xx]][, (mm) := as.list(rep(NA_real_, length(mm)))]
  }
  # put columns in correct order
  setcolorder(cc[[xx]], full) 
  }
}

 cdt <- rbindlist(cc)
})

#   user  system elapsed 
# 21.83    0.06   22.00 

This second solution has been left here to show how data.table can be used poorly.