转换数据框元素中的列表元素

Question

I have these data:

a <- data.frame(element1 = c("JB", "AC", "DO", "MR"),
                element2 = c(1, 3, 4, 2))

b <- list(JB = c("a", "b", "s"), DO = c("ER", "TR", "OP"))

I want to create a new data frame ab similar to data frame a , but such that the elements of the first column are the elements of the list b. Ie in the new ab data frame, the elements of the first column that have the same title as the elements of the list b take the value of the elements in the list b .

EDIT : The output should be the same as a, but with element1 elements being lists:

> ab
  element1 element2
1       JB        1
2       AC        3
3       DO        4
4       MR        2

Answer 1

a <- data.frame(element1 = c("JB", "AC", "DO", "MR"),
            element2 = c(1, 3, 4, 2))

b <- data.frame(JB = c("a", "b", "s"), DO = c("ER", "TR", "OP"))

merge(b,a)

This should do the job. Output will be:

   JB DO element1 element2
1   a ER       JB        1
2   b TR       JB        1
3   s OP       JB        1
4   a ER       AC        3
5   b TR       AC        3
6   s OP       AC        3
7   a ER       DO        4
8   b TR       DO        4
9   s OP       DO        4
10  a ER       MR        2
11  b TR       MR        2
12  s OP       MR        2

Answer 2

Isn't that just

ab <- within(a, element1 <- b[element1])

Output

> str(ab)
'data.frame':   4 obs. of  2 variables:
 $ element1:List of 4
  ..$ JB: chr  "a" "b" "s"
  ..$ NA: NULL
  ..$ DO: chr  "ER" "TR" "OP"
  ..$ NA: NULL
 $ element2: num  1 3 4 2