> matrix(rep(3,8), nrow=4)
[,1] [,2]
[1,] 3 3
[2,] 3 3
[3,] 3 3
[4,] 3 3
> matrix(3, nrow=4, ncol=3)
[,1] [,2] [,3]
[1,] 3 3 3
[2,] 3 3 3
[3,] 3 3 3
[4,] 3 3 3
> w=matrix(0, nrow=3, ncol=4)
> w
[,1] [,2] [,3] [,4]
[1,] 0 0 0 0
[2,] 0 0 0 0
[3,] 0 0 0 0
> w[2,3]=5
> w
[,1] [,2] [,3] [,4]
[1,] 0 0 0 0
[2,] 0 0 5 0
[3,] 0 0 0 0
>
> x=matrix(1:12, nrow=3, ncol=4)
> x
[,1] [,2] [,3] [,4]
[1,] 1 4 7 10
[2,] 2 5 8 11
[3,] 3 6 9 12
> dim(x)
[1] 3 4
> y = 1:12
> y %*% x
錯誤在y %*% x : 非調和引數
> y = 1:3
> y %*% x
[,1] [,2] [,3] [,4]
[1,] 14 32 50 68
> t(x)
[,1] [,2] [,3]
[1,] 1 2 3
[2,] 4 5 6
[3,] 7 8 9
[4,] 10 11 12
> diag(c(3,7,2))
[,1] [,2] [,3]
[1,] 3 0 0
[2,] 0 7 0
[3,] 0 0 2
> diag(x)
[1] 1 5 9
> det(x)
錯誤在determinant.matrix(x, logarithm = TRUE, ...) :
'x' must be a square matrix
> z = matrix(1:9, nrow=3, ncol=3)
> det(z)
[1] 0
> z
[,1] [,2] [,3]
[1,] 1 4 7
[2,] 2 5 8
[3,] 3 6 9
> z[2,1]=10
> z
[,1] [,2] [,3]
[1,] 1 4 7
[2,] 10 5 8
[3,] 3 6 9
> det(z)
[1] 48
> eigen(z)
$values
[1] 17.936765+0.000000i -1.468383+0.721055i -1.468383-0.721055i
$vectors
[,1] [,2] [,3]
[1,] 0.4100596+0i 0.2162169-0.1118877i 0.2162169+0.1118877i
[2,] 0.6875542+0i -0.8668747+0.0000000i -0.8668747+0.0000000i
[3,] 0.5992665+0i 0.4306386+0.0617265i 0.4306386-0.0617265i
> x
[,1] [,2] [,3] [,4]
[1,] 1 4 7 10
[2,] 2 5 8 11
[3,] 3 6 9 12
> rownames(x) = paste("r", 1:3, sep="_")
> x
[,1] [,2] [,3] [,4]
r_1 1 4 7 10
r_2 2 5 8 11
r_3 3 6 9 12
> colnames(x) = paste("c", 1:4, sep="")
> x
c1 c2 c3 c4
r_1 1 4 7 10
r_2 2 5 8 11
r_3 3 6 9 12
>
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