r - List of different length vectors to dataframe -

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i trying convert list of vectors differing lengths dataframe using sapply -

lst = list(c(1, 2, 3), c(4, 5), c(2, 7, 3))  rand = sapply(lst, function(x) {length(x) = 3}) 

but gives me output -

rand [1] 3 3 3 

whereas want -

[[1]]   [1] 1 2 3  [[2]]   [1] 4 5 na  [[3]]   [1] 2 7 3