在R中创建身份矩阵 [英] Creating Identity Matrices in R
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问题描述
我想创建不同大小的身份矩阵,并且可以像这样在较小的规模上做到这一点:
I'd like to create identity matrices of different sizes, and I'm able to do so on a smaller scale like so:
> x <- matrix(cbind(c(1,0), c(0,1)), 2)
> x
[,1] [,2]
[1,] 1 0
[2,] 0 1
就像这样:
> y <- matrix(cbind(c(1,0,0), c(0,1,0), c(0,0,1)), 3)
> y
[,1] [,2] [,3]
[1,] 1 0 0
[2,] 0 1 0
[3,] 0 0 1
但是,随着身份矩阵的大小增加,这似乎将变得越来越乏味.
However, it seems this will become increasingly tedious as identity matrices increase in size.
是否有更简单的方法来创建 n 个值身份矩阵?
Is there an easier way to create n-value identity matrices?
推荐答案
指定nrow
或x
是长度为1的向量时,diag
的一种(两种)用途矩阵
one (two) of the uses for diag
when nrow
is specified or when x
is a vector of length one, you get an identity matrix
diag(5)
diag(nrow = 5)
或者您可以创建一个0s矩阵并填写对角线:
or you could create a matrix of 0s and fill in the diagonal:
mat <- matrix(0, 5, 5)
diag(mat) <- 1
## or shorter:
`diag<-`(matrix(0, 5, 5), 1)
所有这些都给我:
# [,1] [,2] [,3] [,4] [,5]
# [1,] 1 0 0 0 0
# [2,] 0 1 0 0 0
# [3,] 0 0 1 0 0
# [4,] 0 0 0 1 0
# [5,] 0 0 0 0 1
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