Say I have a list of vectors like this:
list.of.vec <- data.frame(id = c(1,2,3,4)) %>%
mutate(a = list(list(c(1,2,3), c(2,3,4)), list(c(2,4,5), c(1,3,4)), list(c(1,2,3), c(4,3,4)), list(c(3,2,3), c(2,3,4))))
how can I arrange a such that in each pair of vectors, the one with the bigger first values goes first? E.g., if there was a list c(1,2,3), c(2,3,4), it should become c(2,3,4), c(1,2,3). And if first values are equal then it looks at the next value.
We can use rrapply
library(rrapply)
library(purrr)
library(dplyr)
list.of.vec <- list.of.vec %>%
mutate(a = map(a, ~ .x[order(-rrapply(.x, f = function(x) x[1],
how = 'unlist'))]))
-output
> list.of.vec
id a
1 1 2, 3, 4, 1, 2, 3
2 2 2, 4, 5, 1, 3, 4
3 3 4, 3, 4, 1, 2, 3
4 4 3, 2, 3, 2, 3, 4
> list.of.vec$a
[[1]]
[[1]][[1]]
[1] 2 3 4
[[1]][[2]]
[1] 1 2 3
[[2]]
[[2]][[1]]
[1] 2 4 5
[[2]][[2]]
[1] 1 3 4
[[3]]
[[3]][[1]]
[1] 4 3 4
[[3]][[2]]
[1] 1 2 3
[[4]]
[[4]][[1]]
[1] 3 2 3
[[4]][[2]]
[1] 2 3 4
You can use -
list.of.vec$a <- lapply(list.of.vec$a, function(x) {
inds <- match(TRUE, x[[1]] != x[[2]])
if(x[[1]][inds] > x[[2]][inds]) x else rev(x)
})
list.of.vec$a
#[[1]]
#[[1]][[1]]
#[1] 2 3 4
#[[1]][[2]]
#[1] 1 2 3
#[[2]]
#[[2]][[1]]
#[1] 2 4 5
#[[2]][[2]]
#[1] 1 3 4
#[[3]]
#[[3]][[1]]
#[1] 4 3 4
#[[3]][[2]]
#[1] 1 2 3
#[[4]]
#[[4]][[1]]
#[1] 3 2 3
#[[4]][[2]]
#[1] 2 3 4
inds would return the index for each list that we need to compare, an index where the value is different in both the vectors. If the first index has a higher value we return the list as it is without any change or else we return the reversed list.
We can try
lapply(
a,
function(x) {
x[order(-sapply(x, `[`, 1))]
}
)
which gives
[[1]]
[[1]][[1]]
[1] 2 3 4
[[1]][[2]]
[1] 1 2 3
[[2]]
[[2]][[1]]
[1] 2 4 5
[[2]][[2]]
[1] 1 3 4
[[3]]
[[3]][[1]]
[1] 4 3 4
[[3]][[2]]
[1] 1 2 3
[[4]]
[[4]][[1]]
[1] 3 2 3
[[4]][[2]]
[1] 2 3 4