生成具有元素1和-1的维k的不同向量

Question

我想计算一个具有k行和2 ^ k列的矩阵(S),以满足以下两个条件:

1) all of whose elements are either 1 or -1 ,
2) each column of S is a vector of dimension k and columns are distinct. 

如何使用R？谢谢.

Answer 1

您可以使用expand.grid,它创建输入向量的所有组合:

k <- 3
t(expand.grid(rep(list(c(1,-1)), k)))
#     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
#Var1    1   -1    1   -1    1   -1    1   -1
#Var2    1    1   -1   -1    1    1   -1   -1
#Var3    1    1    1    1   -1   -1   -1   -1