We get the length of list element ('indx') by looping with sapply. In the recent version of R, we can use lengths to replace the sapply(.., length) step. We change the length of each element to the max length from the 'indx' (length<-) and thereby pad NA values at the end of the list elements with length less than the max length. We can rbind the list elements, convert to data.frame and change the column names.
indx <- sapply(lst, length)
#indx <- lengths(lst)
res <- as.data.frame(do.call(rbind,lapply(lst, `length<-`,
max(indx))))
colnames(res) <- names(lst[[which.max(indx)]])
res
# sk ques pval diff imp
#1 10 sfsf 0.05 <NA> <NA>
#2 24 wwww 0.11 0.3 <NA>
#3 24 wwww 0.11 0.3 2
data
lst <- list(structure(c("10", "sfsf", "0.05"), .Names = c("sk", "ques",
"pval")), structure(c("24", "wwww", "0.11", "0.3"), .Names = c("sk",
"ques", "pval", "diff")), structure(c("24", "wwww", "0.11", "0.3",
"2"), .Names = c("sk", "ques", "pval", "diff", "imp")))
