将字符串与R中的combn列表组合

我想循环使用

combn（）

创建的组合

输入：

"a" "b" "c" "d"

期望输出：

[1] "a" "b" "c" "d"
[1] "a and b" "a and c" "a and d" "b and c" "b and d" "c and d"
[1] "a and b and c" "a and b and d" "a and c and d" "b and c and d"
[1] "a and b and c and d"

我的尝试：

classes <- letters[1:4]
cl <- lapply(1:length(classes), combn, x = classes)
apply(cl[[1]], 2, paste, collapse = " and ")
apply(cl[[2]], 2, paste, collapse = " and ")
apply(cl[[3]], 2, paste, collapse = " and ")
apply(cl[[4]], 2, paste, collapse = " and ")

---

classes您可以迭代向量的长度，并使用
combn（）
的函数参数使用
paste（）
折叠输出：

vec Bingo，
combn（）
有一个经常被忽略的
FUN=
参数，它适用于每个组合。这就是我想写的。从未注意到函数参数。谢谢！
vec <- letters[1:4]

lapply(seq_along(vec), function(x) combn(vec, x, FUN = paste, collapse = " and "))

[[1]]
[1] "a" "b" "c" "d"

[[2]]
[1] "a and b" "a and c" "a and d" "b and c" "b and d" "c and d"

[[3]]
[1] "a and b and c" "a and b and d" "a and c and d" "b and c and d"

[[4]]
[1] "a and b and c and d"