Convert a list to a data frame

I have a nested list of data. Its length is 132 and each item is a list of length 20. Is there a quick way to convert this structure into a data frame that has 132 rows and 20 columns of data?

Here is some sample data to work with:

l <- replicate(
  132,
  as.list(sample(letters, 20)),
  simplify = FALSE
)

With rbind

do.call(rbind.data.frame, your_list)

Edit: Previous version return data.frame of list's instead of vectors (as @IanSudbery pointed out in comments).

Update July 2020:

The default for the parameter stringsAsFactors is now default.stringsAsFactors() which in turn yields FALSE as its default.

Assuming your list of lists is called l:

df <- data.frame(matrix(unlist(l), nrow=length(l), byrow=TRUE))

The above will convert all character columns to factors, to avoid this you can add a parameter to the data.frame() call:

df <- data.frame(matrix(unlist(l), nrow=132, byrow=TRUE),stringsAsFactors=FALSE)

You can use the plyr package. For example a nested list of the form

l <- list(a = list(var.1 = 1, var.2 = 2, var.3 = 3)
      , b = list(var.1 = 4, var.2 = 5, var.3 = 6)
      , c = list(var.1 = 7, var.2 = 8, var.3 = 9)
      , d = list(var.1 = 10, var.2 = 11, var.3 = 12)
      )

has now a length of 4 and each list in l contains another list of the length 3. Now you can run

  library (plyr)
  df <- ldply (l, data.frame)

and should get the same result as in the answer @Marek and @nico.

Fixing the sample data so it matches the original description 'each item is a list of length 20'

mylistlist <- replicate(
  132,
  as.list(sample(letters, 20)),
  simplify = FALSE
)

we can convert it to a data frame like this:

data.frame(t(sapply(mylistlist,c)))

sapply converts it to a matrix. data.frame converts the matrix to a data frame.

resulting in:

assume your list is called L,

data.frame(Reduce(rbind, L))