我正在尝试获取变量元素长度3的所有可能组合。尽管它部分地与combn()一起工作,但我并未完全获得所需的输出。这是我的示例
x <- c("a","b","c","d","e")
t(combn(c(x,x), 3))
我得到的输出看起来像这样
[,1] [,2] [,3]
[1,] "a" "b" "c"
[2,] "a" "b" "d"
[3,] "a" "b" "e"
我对这个命令并不满意,原因有两个。我想得到一个输出内容为“ a + b + c”,“ a + b + b” ....,很遗憾,我无法使用paste()或其他内容来编辑输出。
我也期待每组字母的一种组合,即我要么得到“ a + b + c”,要么得到“ b + a + c”,但不能同时获得两者。
尝试类似的东西:
x <- c("a","b","c","d","e")
d1 <- combn(x,3) # All combinations
d1
# [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
# [1,] "a" "a" "a" "a" "a" "a" "b" "b" "b" "c"
# [2,] "b" "b" "b" "c" "c" "d" "c" "c" "d" "d"
# [3,] "c" "d" "e" "d" "e" "e" "d" "e" "e" "e"
nrow(unique(t(d1))) == nrow(t(d1))
# [1] TRUE
d2 <- expand.grid(x,x,x) # All permutations
d2
# Var1 Var2 Var3
# 1 a a a
# 2 b a a
# 3 c a a
# 4 d a a
# 5 e a a
# 6 a b a
# 7 b b a
# 8 c b a
# 9 d b a
# ...
nrow(unique(d2)) == nrow(d2)
# [1] TRUE
尝试一下
x <- c("a","b","c","d","e")
expand.grid(rep(list(x), 3))