Building a list in a loop in R - getting item names correct

Question

I have a function which contains a loop over two lists and builds up some calculated data. I would like to return these data as a lists of lists, indexed by some value, but

Answer 1

To show that an explicit for loop is not required

unif_norm  <- replicate(5, list(uniform = runif(10),
  normal = rnorm(16)), simplify=F)

binomials <- lapply(seq_len(5)/10, function(prob) {
 list(binomial =  rbinom(n = 5 ,size = 8, prob = prob))})

biglist <- setNames(mapply(c, unif_norm, binomials, SIMPLIFY = F), 
                     paste0('item:',seq_along(unif_norm)))

In general if you go down the for loop path it is better to preassign the list beforehand. This is more memory efficient.

mybiglist <- vector('list', 5)
names(mybiglist) <- paste0('item:', seq_along(mybiglist))
for(i in seq_along(mybiglist)){
    a <- runif(10)
    b <- rnorm(16)
    c <- rbinom(8, 5, i/10)

    tmp <- list(uniform=a, normal=b, binomial=c)
    mybiglist[[i]] <- tmp
}

Answer 2

Change

mybiglist[[name]] <- append(mybiglist, tmp)

to

mybiglist[[name]] <- tmp

Answer 3

It works if you don't use the append command:

mybiglist <- list()
for(i in 1:5){
  a <- runif(10)
  b <- rnorm(16)
  c <- rbinom(8, 5, i/10)
  name <- paste('item:',i,sep='')
  tmp <- list(uniform=a, normal=b, binomial=c)
  mybiglist[[name]] <- tmp
}

# List of 5
# $ item:1:List of 3
# ..$ uniform : num [1:10] 0.737 0.987 0.577 0.814 0.452 ...
# ..$ normal  : num [1:16] -0.403 -0.104 2.147 0.32 1.713 ...
# ..$ binomial: num [1:8] 0 0 0 0 1 0 0 1
# $ item:2:List of 3
# ..$ uniform : num [1:10] 0.61 0.62 0.49 0.217 0.862 ...
# ..$ normal  : num [1:16] 0.945 -0.154 -0.5 -0.729 -0.547 ...
# ..$ binomial: num [1:8] 1 2 2 0 2 1 0 2
# $ item:3:List of 3
# ..$ uniform : num [1:10] 0.66 0.094 0.432 0.634 0.949 ...
# ..$ normal  : num [1:16] -0.607 0.274 -1.455 0.828 -0.73 ...
# ..$ binomial: num [1:8] 2 2 3 1 1 1 2 0
# $ item:4:List of 3
# ..$ uniform : num [1:10] 0.455 0.442 0.149 0.745 0.24 ...
# ..$ normal  : num [1:16] 0.0994 -0.5332 -0.8131 -1.1847 -0.8032 ...
# ..$ binomial: num [1:8] 2 3 1 1 2 2 2 1
# $ item:5:List of 3
# ..$ uniform : num [1:10] 0.816 0.279 0.583 0.179 0.321 ...
# ..$ normal  : num [1:16] -0.036 1.137 0.178 0.29 1.266 ...
# ..$ binomial: num [1:8] 3 4 3 4 4 2 2 3