R：通过删除和添加循环变量来迭代向量

考虑一个向量：

---

dim如果您正在查找
dim
的所有组合，可以从
combinat
软件包中查看功能
combn
：

combinat::combn(letters[1:4], 1, simplify = F)

    [[1]]
[1] "a"

[[2]]
[1] "b"

[[3]]
[1] "c"

[[4]]
[1] "d"

combinat::combn(letters[1:4], 2, simplify = F)
combinat::combn(letters[1:4], 3, simplify = F)
combinat::combn(letters[1:4], 4, simplify = F)

在base
R
中，我将使用
for
-循环、
sapply
或
lappy

用于
-循环

for (i in seq_along(dim)) {
  print(dim[-i])
}

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

sapply

t( sapply(seq_along(dim), function(i) dim[-i]) )

     [,1] [,2] [,3]
[1,] "b"  "c"  "d" 
[2,] "a"  "c"  "d" 
[3,] "a"  "b"  "d" 
[4,] "a"  "b"  "c" 

lapply(seq_along(dim), function(i) dim[-i])

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

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

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

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

lappy

t( sapply(seq_along(dim), function(i) dim[-i]) )

     [,1] [,2] [,3]
[1,] "b"  "c"  "d" 
[2,] "a"  "c"  "d" 
[3,] "a"  "b"  "d" 
[4,] "a"  "b"  "c" 

lapply(seq_along(dim), function(i) dim[-i])

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

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

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

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

您可以通过以下方式获得：

dim <- c("a", "b", "c", "d")
> Map(combn, list(dim), 1:length(dim))

[[1]]  # All combinations of size 1
     [,1] [,2] [,3] [,4]
[1,] "a"  "b"  "c"  "d" 

[[2]]  # All combinations of size 2
     [,1] [,2] [,3] [,4] [,5] [,6]
[1,] "a"  "a"  "a"  "b"  "b"  "c" 
[2,] "b"  "c"  "d"  "c"  "d"  "d" 

[[3]]  # All combinations of size 3
     [,1] [,2] [,3] [,4]
[1,] "a"  "a"  "a"  "b" 
[2,] "b"  "b"  "c"  "c" 
[3,] "c"  "d"  "d"  "d" 

[[4]]  # All combinations of size 4
     [,1]
[1,] "a" 
[2,] "b" 
[3,] "c" 
[4,] "d" 

尺寸图（梳，列表（尺寸），1：长度（尺寸））
[[1]]#大小为1的所有组合
[,1] [,2] [,3] [,4]
[1，]a“b”c“d”
[[2]]#大小为2的所有组合
[,1] [,2] [,3] [,4] [,5] [,6]
[1，]a“a”a“b”b“c”
[2，][b”“c”“d”“c”“d”“d”
[[3]]#所有大小为3的组合
[,1] [,2] [,3] [,4]
[1，]a“a”a“b”
[2，]b“b”c“c”
[3，]“c”“d”“d”
[[4]]#所有大小为4的组合
[,1]
[1，]“a”
[2，]“b”
[3，]“c”
[4，]“d”
您是否在寻找
c（“a”、“b”、“c”、“d”）的所有排列方式
？是的！我相信所以我想你可能指的是所有的子集：或者？是的，我指的是所有的子集。但是这些问题产生了幂集而不是子集幂集是所有子集的集合，对吗？如果您只需要严格的子集，第二个链接中的James answer可以进行调整，如
lappy（1:（长度（dim）-1），function（x）combn（dim，x））
我不关心顺序，我不希望重复相同的4个元素。我想要像
[[1]][1]“a”“b”[[2]][1]“a”“b”“c”好的，我明白了，您正在寻找组合：）。我编辑了我的答案