list of lists with different lengths to data.frame in R

Question

I have read many answers in SO about converting list of lists to df. But, I have noticed that they all have the length of lists (within the main big list) to be the same. I have a different case:

h1 <- list(USA = c(10,13,17,11), RUSSIA = NULL, BRAZIL = NULL,
  CHINA = c(11,11,10,8,12), TAIWAN = c(12,9,9,11,9,12,14), CHILE = NULL)

I want to convert the above list h1 to a data.frame. My expected output should be a data.frame that has 2 columns - country_name, list. Something like this:

country_name, list
USA    [10, 13, 17, 11]
RUSSIA NULL
BRAZIL NULL
CHINA  [11, 11, 10, 8, 12]
TAIWAN [12, 9, 9, 11, 9, 12, 14]
CHILE  NULL

I did the follwing, but, did not work:

do.call(rbind, h1)

It tries to keep the column numbers same across all the rows. I do not want that. I want to see how I can use ldply to such cases. Any suggestion is appreciated.

Answer 1

Here's one way:

R> as.data.frame(as.matrix(h1))
                            V1
USA             10, 13, 17, 11
RUSSIA                    NULL
BRAZIL                    NULL
CHINA        11, 11, 10, 8, 12
TAIWAN 12, 9, 9, 11, 9, 12, 14
CHILE                     NULL

R> as.data.frame(as.matrix(h1))['TAIWAN', ]
$TAIWAN
[1] 12  9  9 11  9 12 14

Answer 2

You can convert a list to a matrix, where every element of the matrix will be a list.

d1 <- data.frame(country_name=names(h1), list=matrix(h1))

That said, I recommend against doing this because it does not fit the R paradigm. Most R functions assume a matrix contains elements from one atomic type.