Appending a list to a list of lists in R

Could it be this, what you want to have:

# Initial list:
myList <- list()

# Now the new experiments
for(i in 1:3){
  myList[[length(myList)+1]] <- list(sample(1:3))
}

myList

There are two other solutions which involve assigning to an index one past the end of the list. Here is a solution that does use append.

resultsa <- list(1,2,3,4,5)
resultsb <- list(6,7,8,9,10)
resultsc <- list(11,12,13,14,15)

outlist <- list(resultsa)
outlist <- append(outlist, list(resultsb))
outlist <- append(outlist, list(resultsc))

which gives your requested format

> str(outlist)
List of 3
 $ :List of 5
  ..$ : num 1
  ..$ : num 2
  ..$ : num 3
  ..$ : num 4
  ..$ : num 5
 $ :List of 5
  ..$ : num 6
  ..$ : num 7
  ..$ : num 8
  ..$ : num 9
  ..$ : num 10
 $ :List of 5
  ..$ : num 11
  ..$ : num 12
  ..$ : num 13
  ..$ : num 14
  ..$ : num 15

outlist <- list(resultsa)
outlist[2] <- list(resultsb)
outlist[3] <- list(resultsc)

append's help file says it is for vectors. But it can be used here. I thought I had tried that before but there were some strange anomalies in the OP's code that may have mislead me:

outlist <- list(resultsa)
outlist <- append(outlist,list(resultsb))
outlist <- append(outlist,list(resultsc))

Same results.