R: Converting nested list to dataframe and get names of list levels als factors

Question

I have a nested list:

list1 <- list("A"=c(1,1,1), "B"=c(2,2,2), "C"=c(3,3,3))
list2 <- list("F1" = list1, "F2" = list1)

and I would like to get the last level of the list (containing the vector) as a dataframe and I would like to get the levels of the list as factors:

  Level1 Level2 V1 V2 V3
1     F1      A  1  1  1
2     F1      B  2  2  2
3     F1      C  3  3  3
4     F2      A  1  1  1
5     F2      B  2  2  2
6     F2      C  3  3  3

The first part is nicely given by:

data.frame(matrix(unlist(list2), ncol=3, byrow=T))

However, I did not find a nice way to also get the list-level-names as factors in the same dataframe. Any ideas? :)

Edit: The procedure should work up to p dimensions.

Answer 1

melt from "reshape2" has a method for lists. Perhaps it can be used in this case. Something like this:

library(reshape2)
dcast(cbind(
  coln = sequence(rapply(list2, length)), 
  melt(list2)), L1 + L2 ~ coln, 
  value.var = "value")
#   L1 L2 1 2 3
# 1 F1  A 1 1 1
# 2 F1  B 2 2 2
# 3 F1  C 3 3 3
# 4 F2  A 1 1 1
# 5 F2  B 2 2 2
# 6 F2  C 3 3 3

Answer 2

You can unlist just one level , than convert rownames to columns, and join the all in a single data.frame:

xx <- do.call(rbind,unlist(list2,recursive = FALSE))
cbind.data.frame(do.call(rbind,strsplit(rownames(xx),'.',fixed=TRUE))
                ,xx)

      1 2 1 2 3
F1.A F1 A 1 1 1
F1.B F1 B 2 2 2
F1.C F1 C 3 3 3
F2.A F2 A 1 1 1
F2.B F2 B 2 2 2
F2.C F2 C 3 3 3