R中载体及其阴性的所有组合

How can I find all combinations of a vector and it's negatives in R?

如何找到矢量的所有组合,它在R中是否为负数?

I.E.

x <- c(1,2,3,4)

will output

(1,2,3,4), (-1,2,3,4), (1,-2,3,4), (1,2,-3,4), (1,2,3,-4), ... , (-1,-2,-3,-4)

3 个解决方案

#1

You could use do.call and expand.grid:

你可以使用do.call和expand.grid:

do.call(expand.grid, lapply(x, function(y) c(y, -y)))
#    Var1 Var2 Var3 Var4
# 1     1    2    3    4
# 2    -1    2    3    4
# 3     1   -2    3    4
# 4    -1   -2    3    4
# 5     1    2   -3    4
# 6    -1    2   -3    4
# 7     1   -2   -3    4
# 8    -1   -2   -3    4
# 9     1    2    3   -4
# 10   -1    2    3   -4
# 11    1   -2    3   -4
# 12   -1   -2    3   -4
# 13    1    2   -3   -4
# 14   -1    2   -3   -4
# 15    1   -2   -3   -4
# 16   -1   -2   -3   -4

The code lapply(1:4, function(x) c(x, -x)) creates a list of each element of your vector and its negative; in your case this would be list(c(1, -1), c(2, -2), c(3, -3), c(4, -4)). Then do.call passes each of these list elements as arguments to expand.grid, which returns all possible combinations.

代码lapply(1:4,function(x)c(x,-x))创建向量的每个元素及其负数的列表;在你的情况下,这将是列表(c(1,-1),c(2,-2),c(3,-3),c(4,-4))。然后do.call将每个列表元素作为参数传递给expand.grid,它返回所有可能的组合。

A slightly simpler way to get the arguments could be to use as.data.frame(rbind(x, -x)) instead of lapply(x, function(y) c(y, -y)).

获取参数的一种稍微简单的方法可以是使用as.data.frame(rbind(x,-x))而不是lapply(x,function(y)c(y,-y))。

#2

Or a variant of @josilber's solution is

或@josilber解决方案的变体是

 expand.grid(Map(c, x, -x))

#3

use library(gtools)

gtools::combinations(8,4, c(-4:-1,1:4))

#1