我想循环查看由创建的组合combn()。
输入：
"a" "b" "c" "d"
所需输出：
[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"
我试过的
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 ")
基本上，我的问题是遍历最后一部分的最佳方法是什么apply(cl[[NR]], 2, paste, collapse = " and ")。
我考虑过了lapply，但是我要分配FUN两次，将lapply组合并应用到一个调用中似乎很奇怪。for循环是可能的，但也许有更有效的方法。
如果该问题更适合代码审查，我很乐意将其迁移。
您可以遍历向量的长度，并使用的函数参数使用以下combn()命令折叠输出paste()：
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"
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