Question

I have a list of vectors whose values are bounded between 1 and 100.

[[1]]
[[1]][[1]]
[1] "a"

[[1]][[2]]
[1] 41  5 53 55 56


[[2]]
[[2]][[1]]
[1] "b"

[[2]][[2]]
[1] 41 1 57 53  48

etc.

How do i somehow get to the following data.frame

  no      1        2
  1      NA        b
  41      a        b
   5      a       NA
  53      a       NA
  55      a       NA
  56      a       NA
  48     NA        b
  57     NA        b
  53     NA        b

and from there fill in the missing rows and ordered according to the column “no” where column no. runs from 1 to 100?
eg.

  no      1        2
  1      NA        b
  2      NA       NA
  3      NA       NA
  4      NA       NA
  5      a        NA

etc.
all the way until the 100th row.

Answer 1

Here is an approach with lapply:

The data:

dat <- list(list("a", c(41, 5, 53, 55, 56)), list("b", c(41, 1, 57, 53, 48)))

The solution:

lev <- 1:100                # the unique numbers
vec <- rep(NA, length(lev)) # a vector full of NAs

data.frame(no = lev,
           setNames(lapply(dat,
                           function(x) "[<-"(vec, lev %in% x[[2]], x[[1]])),
                    seq_along(dat)), check.names = FALSE)

The output (the first 10 rows):

     no    1    2
1     1 <NA>    b
2     2 <NA> <NA>
3     3 <NA> <NA>
4     4 <NA> <NA>
5     5    a <NA>
6     6 <NA> <NA>
7     7 <NA> <NA>
8     8 <NA> <NA>
9     9 <NA> <NA>
10   10 <NA> <NA>