Named List To/From Data.Frame

Another option is enframe from tibble

library(tidyverse)
enframe(lst1) %>%
   unnest

data

lst1 <- list(a=1:3, b=4:6)

Use stack and unstack in base R:

x <- data.frame(a=1:3, b=4:6)

x
  a b
1 1 4
2 2 5
3 3 6

Use stack to from wide to tall, i.e. stack the vectors on top of one another.

y <- stack(x)
y
  values ind
1      1   a
2      2   a
3      3   a
4      4   b
5      5   b
6      6   b

Use unstack to do the reverse.

unstack(y)
  a b
1 1 4
2 2 5
3 3 6

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If your data structure is more complicated than you described, stack and unstack may no longer be suitable. In that case you'll have to use reshape in base R, or melt and dcast in package reshape2.