> a=diag(4)+1
> a
[,1] [,2] [,3] [,4]
[1,] 2 1 1 1
[2,] 1 2 1 1
[3,] 1 1 2 1
[4,] 1 1 1 2
> a.e=eigen(a,symmetric=T)
> a.e
eigen() decomposition
$`values`
[1] 5 1 1 1
$vectors
[,1] [,2] [,3] [,4]
[1,] -0.5 0.8660254 0.0000000 0.0000000
[2,] -0.5 -0.2886751 -0.5773503 -0.5773503
[3,] -0.5 -0.2886751 -0.2113249 0.7886751
[4,] -0.5 -0.2886751 0.7886751 -0.2113249
>a.e$vectors%*%diag(a.e$values)%*%t(a.e$vectors)
[,1] [,2] [,3] [,4]
[1,] 2 1 1 1
[2,] 1 2 1 1
[3,] 1 1 2 1
[4,] 1 1 1 2
最後一個是