| transpose {purrr} | R Documentation |
Tranpose turns a list-of-lists "inside-out"; it turns a pair of lists into a
list of pairs, or a list of pairs into pair of lists. For example,
If you had a list of length n where each component had values a and
b, transpose() would make a list with elements a and
b that contained lists of length n. It's called transpose because
x[[1]][[2]] is equivalent to transpose(x)[[2]][[1]].
transpose(.l)
.l |
A list of vectors to zip. The first element is used as the template; you'll get a warning if a sub-list is not the same length as the first element. For efficiency, elements are matched by position, not by name. |
Note that transpose() is its own inverse, much like the
transpose operation on a matrix. You can get back the original
input by transposing it twice.
x <- rerun(5, x = runif(1), y = runif(5))
x %>% str()
x %>% transpose() %>% str()
# Back to where we started
x %>% transpose() %>% transpose() %>% str()
# transpose() is useful in conjunction with safely() & quietly()
x <- list("a", 1, 2)
y <- x %>% map(safely(log))
y %>% str()
y %>% transpose() %>% str()
# Use simplify_all() to reduce to atomic vectors where possible
x <- list(list(a = 1, b = 2), list(a = 3, b = 4), list(a = 5, b = 6))
x %>% transpose()
x %>% transpose() %>% simplify_all()