R语言学习笔记-矩阵的创建与操作方法

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一、创建矩阵

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# 创建两个数字变量
var5=sample(31:60,25,replace=T)
var6=sample(1:30,25,replace=T)
# 创建两个5行5列的矩阵，创建5行5列的矩阵的原因，是为了方便说明问题；
A <- matrix(var5,nrow=5)
B <- matrix(var6,nrow=5)
> A
[,1] [,2] [,3] [,4] [,5]
[1,]   43   32   54   41   56
[2,]   56   45   37   57   38
[3,]   50   50   40   32   50
[4,]   34   56   49   36   42
[5,]   56   41   33   40   46
> B
[,1] [,2] [,3] [,4] [,5]
[1,]   18   21   23    1   18
[2,]   18    5   23   10    5
[3,]   26    6   26    8   26
[4,]    7    5    7   16   15
[5,]   29   20    1   15    2

二、操作矩阵

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# 结合矩阵A与B的行，A先B后；
C <- rbind(A,B)
# 结合矩阵A与B的行，B先A后；
D <- rbind(B,A)
# 结合矩阵A与B的列，A先B后；
E <- cbind(A,B)
# 结合矩阵A与B的列，B先A后；
F <- cbind(B,A)
> C
[,1] [,2] [,3] [,4] [,5]
[1,]   43   32   54   41   56
[2,]   56   45   37   57   38
[3,]   50   50   40   32   50
[4,]   34   56   49   36   42
[5,]   56   41   33   40   46
[6,]   18   21   23    1   18
[7,]   18    5   23   10    5
[8,]   26    6   26    8   26
[9,]    7    5    7   16   15
[10,]   29   20    1   15    2
> D
[,1] [,2] [,3] [,4] [,5]
[1,]   18   21   23    1   18
[2,]   18    5   23   10    5
[3,]   26    6   26    8   26
[4,]    7    5    7   16   15
[5,]   29   20    1   15    2
[6,]   43   32   54   41   56
[7,]   56   45   37   57   38
[8,]   50   50   40   32   50
[9,]   34   56   49   36   42
[10,]   56   41   33   40   46
> E
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,]   43   32   54   41   56   18   21   23    1    18
[2,]   56   45   37   57   38   18    5   23   10     5
[3,]   50   50   40   32   50   26    6   26    8    26
[4,]   34   56   49   36   42    7    5    7   16    15
[5,]   56   41   33   40   46   29   20    1   15     2
> F
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,]   18   21   23    1   18   43   32   54   41    56
[2,]   18    5   23   10    5   56   45   37   57    38
[3,]   26    6   26    8   26   50   50   40   32    50
[4,]    7    5    7   16   15   34   56   49   36    42
[5,]   29   20    1   15    2   56   41   33   40    46

# 选取矩阵A中的单个元素
> A[2,3]
[1] 37
# 选取整行；
> A[3,]
[1] 50 50 40 32 50
# 选取整列；
> A[,5]
[1] 56 38 50 42 46
# 选取多行，注意：生成的新矩阵行号改变；
> A[c(3,4),]
[,1] [,2] [,3] [,4] [,5]
[1,]   50   50   40   32   50
[2,]   34   56   49   36   42
# 选取多列，注意：生成的新矩阵列号改变；
> A[,c(1,3,5)]
[,1] [,2] [,3]
[1,]   43   54   56
[2,]   56   37   38
[3,]   50   40   50
[4,]   34   49   42
[5,]   56   33   46
# 更改矩阵B的行名与列名；
> dimnames(B)=list(c("R1","R2","R3","R4","R5"),c("C1","C2","C3","C4","C5"))
> B
C1 C2 C3 C4 C5
R1 18 21 23  1 18
R2 18  5 23 10  5
R3 26  6 26  8 26
R4  7  5  7 16 15
R5 29 20  1 15  2
# 对矩阵的行和列进行命名后，可以通过行名与列名操作矩阵；
# 选取单个元素；
> B["R4","C5"]
[1] 15
# 选取整行；
> B["R3",]
C1 C2 C3 C4 C5 
26  6 26  8 26
# 选取整列；
> B[,"C2"]
R1 R2 R3 R4 R5 
21  5  6  5 20
# 选取多行；
> B[c("R1","R2","R4"),]
C1 C2 C3 C4 C5
R1 18 21 23  1 18
R2 18  5 23 10  5
R4  7  5  7 16 15
# 选取多列；
> B[,c("C3","C5")]
C3 C5
R1 23 18
R2 23  5
R3 26 26
R4  7 15
R5  1  2
# 对矩阵C进行行列转置(transpose)；
> G <- t(C)
> G
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,]   43   56   50   34   56   18   18   26    7    29
[2,]   32   45   50   56   41   21    5    6    5    20
[3,]   54   37   40   49   33   23   23   26    7     1
[4,]   41   57   32   36   40    1   10    8   16    15
[5,]   56   38   50   42   46   18    5   26   15     2
# 解构矩阵(Deconstruction);
>H <- c(D)
> H
[1] 18 18 26  7 29 43 56 50 34 56 21  5  6  5 20 32 45 50 56 41 23 23 26  7  1
[26] 54 37 40 49 33  1 10  8 16 15 41 57 32 36 40 18  5 26 15  2 56 38 50 42 46
# 解构之后就不是矩阵了；
> class(D)
[1] "matrix"
> class(H)
[1] "integer"
# 转换矩阵E为数据框；
I <- as.data.frame(E)
> I <- as.data.frame(E)
> I
V1 V2 V3 V4 V5 V6 V7 V8 V9 V10
1 43 32 54 41 56 18 21 23  1  18
2 56 45 37 57 38 18  5 23 10   5
3 50 50 40 32 50 26  6 26  8  26
4 34 56 49 36 42  7  5  7 16  15
5 56 41 33 40 46 29 20  1 15   2
# 先看看E的数据类型；
> class(E)
[1] "matrix"
> mode(E)
[1] "numeric"
> typeof(E)
[1] "integer"
# 再看一下I，转变成数据框；
> class(I)
[1] "data.frame"
> mode(I)
[1] "list"
> typeof(I)
[1] "list"
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