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()