訊息
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範例一
> d <- seq(1,25,1)
> matrix(d, nrow=5, ncol=5, byrow=T)
[,1] [,2] [,3] [,4] [,5]
[1,] 1 2 3 4 5
[2,] 6 7 8 9 10
[3,] 11 12 13 14 15
[4,] 16 17 18 19 20
[5,] 21 22 23 24 25
> d
[1] 1 2 3 4 5 6 7 8 9 10 11 12 13 14
[15] 15 16 17 18 19 20 21 22 23 24 25
> m = matrix(d, nrow=5, ncol=5, byrow=T)
> m
[,1] [,2] [,3] [,4] [,5]
[1,] 1 2 3 4 5
[2,] 6 7 8 9 10
[3,] 11 12 13 14 15
[4,] 16 17 18 19 20
[5,] 21 22 23 24 25
> m[1,]
[1] 1 2 3 4 5
> m[2,2]
[1] 7
> m[2,1:5]
[1] 6 7 8 9 10
> m[1:5, 2]
[1] 2 7 12 17 22
> m[2, c(1,3,5)]
[1] 6 8 10
> m[c(1,3,5), 2]
[1] 2 12 22
> m[2, -c(1,3,5)]
[1] 7 9
>
範例二
> x = c(1,2,3,4,5,6)
> attr(x, "dim")<-c(2,3)
> x
[,1] [,2] [,3]
[1,] 1 3 5
[2,] 2 4 6
>
> y = c(1,2,3,4)
> dim(y) = c(2,2) # 矩陣其實是二維陣列，向量只有在
> y
[,1] [,2]
[1,] 1 3
[2,] 2 4
>
範例三
> x <- array(1:20, dim=c(4,5))
> x
[,1] [,2] [,3] [,4] [,5]
[1,] 1 5 9 13 17
[2,] 2 6 10 14 18
[3,] 3 7 11 15 19
[4,] 4 8 12 16 20
> i <- array(c(1:3,3:1), dim=c(3,2))
> i
[,1] [,2]
[1,] 1 3
[2,] 2 2
[3,] 3 1
> x[i]
[1] 9 6 3
> x[i] <- 0
> x
[,1] [,2] [,3] [,4] [,5]
[1,] 1 5 0 13 17
[2,] 2 0 10 14 18
[3,] 0 7 11 15 19
[4,] 4 8 12 16 20
>
範例四：
> 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
>
相關套件
- Matrix — http://cran.r-project.org/web/packages/Matrix/index.html
- 稀疏矩陣 — http://cran.r-project.org/web/packages/SparseM/index.html
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