diag

3×3の対角行列を生成する

> diag(3)
     [,1] [,2] [,3]
[1,]    1    0    0
[2,]    0    1    0
[3,]    0    0    1

3×3の対角行列を生成し、対角成分を更新する

# 3x3の行列を生成する
> a <- matrix(c(0,1,2,3,4,5,6,7,9), 3,3)
> a
     [,1] [,2] [,3]
[1,]    0    3    6
[2,]    1    4    7
[3,]    2    5    9

# 対角成分を取得する
> diag(a)
[1] 0 4 9

#対角成分を入れ替える
> diag(a) <- 0
> a
     [,1] [,2] [,3]
[1,]    0    3    6
[2,]    1    0    7
[3,]    2    5    0