91、R语言编程基础

1、查看当前工作空间

> getwd()
[] "C:/Users/P0079482.HHDOMAIN/Documents"
> 

2、查看内存中有哪些对象

> ls()
 [] "a"         "a1"        "b"         "bank"      "bank_full" "dat"
 [] "m1"        "tab"       "w"         "x"         "x1"        "x2"
> 

3、把指定对象从内存中删除

> rm('a')
> ls()
 [] "a1"        "b"         "bank"      "bank_full" "dat"       "m1"
 [] "tab"       "w"         "x"         "x1"        "x2"
> 

4、查看函数帮助

> help(matrix)
> 

5、创建向量和矩阵

> x1=c(2,4,6,8,0)
> x2=c(1,3,5,7,9)
查看向量的长度
> length(x1)
[] 5
查看向量的类型
> mode(x1)
[] "numeric"
> 

6、按行将向量排列成矩阵

> rbind(x1,x2)
[,1] [,2] [,3] [,4] [,5]
x1 2 4 6 8 0
x2 1 3 5 7 9

7、按列将向量排成矩阵

> cbind(x1,x2)
     x1 x2
[1,]  2  1
[2,]  4  3
[3,]  6  5
[4,]  8  7
[5,]  0  9

8、求向量的均值

> x=c(1:100)
> mean(x)
[] 50.5
> 

9、求向量的和

> sum(x)
[] 5050
> 

10、

> max(x)  求最大值
[] 100
> min(x)　　最小值
[] 1
> var(x)　　方差
[] 841.6667
> prod(x)    连乘
[] 9.332622e+157
> sd(x)      标准差
[] 29.01149

11、生成矩阵

> a1=c(1:12)
> matrix(a1,nrow=3,ncol=4)
     [,1] [,2] [,3] [,4]
[1,]    1    4    7   10
[2,]    2    5    8   11
[3,]    3    6    9   12
> 

> matrix(a1,nrow=4,ncol=3)
     [,1] [,2] [,3]
[1,]    1    5    9
[2,]    2    6   10
[3,]    3    7   11
[4,]    4    8   12

> matrix(a1,nrow=4,ncol=3,byrow=T)
     [,1] [,2] [,3]
[1,]    1    2    3
[2,]    4    5    6
[3,]    7    8    9
[4,]   10    1    2

根据行生成矩阵

12、矩阵的转置

> a=matrix(1:12,nrow=3,ncol=4)
> a
     [,1] [,2] [,3] [,4]
[1,]    1    4    7   10
[2,]    2    5    8   11
[3,]    3    6    9   12
> t(a)
     [,1] [,2] [,3]
[1,]    1    2    3
[2,]    4    5    6
[3,]    7    8    9
[4,]   10   11   12
> 

13、矩阵的加减

> a=b=matrix(1:12,nrow=3,ncol=4)
> a+b
     [,1] [,2] [,3] [,4]
[1,]    2    8   14   20
[2,]    4   10   16   22
[3,]    6   12   18   24
> a-b
     [,1] [,2] [,3] [,4]
[1,]    0    0    0    0
[2,]    0    0    0    0
[3,]    0    0    0    0
> 

14、矩阵乘法

> a=matrix(1:12,nrow=3,ncol=4)
> b=matrix(1:12,nrow=4,ncol=3)
> a%*%b
     [,1] [,2] [,3]
[1,]   70  158  246
[2,]   80  184  288
[3,]   90  210  330
> 

15、矩阵求对角元素

> a=matrix(1:16,nrow=4,ncol=4)
> a
     [,1] [,2] [,3] [,4]
[1,]    1    5    9   13
[2,]    2    6   10   14
[3,]    3    7   11   15
[4,]    4    8   12   16
> diag(a)
[]  1  6 11 16
> diag(diag(a))
     [,1] [,2] [,3] [,4]
[1,]    1    0    0    0
[2,]    0    6    0    0
[3,]    0    0   11    0
[4,]    0    0    0   16
> diag(4)
     [,1] [,2] [,3] [,4]
[1,]    1    0    0    0
[2,]    0    1    0    0
[3,]    0    0    1    0
[4,]    0    0    0    1
> 

16、生成随机矩阵

> a=matrix(rnorm(16),4,4)
> a
           [,1]         [,2]        [,3]       [,4]
[1,]  0.2353978 -1.168817665 -0.03914636 -0.4350940
[2,]  0.5550182 -0.001076645 -1.92283070  1.1007430
[3,]  0.2582714 -0.846160178  0.94940298 -0.6125362
[4,] -2.1307575 -2.478207744 -0.44198013 -0.2581712
> 

17、矩阵求逆

> solve(a)
           [,1]       [,2]       [,3]       [,4]
[1,]  0.2524842  0.3182516  0.5172485 -0.2958290
[2,]  0.4128992 -0.5045100 -1.1071800 -0.2200014
[3,] -1.7116774  0.4246262  1.9141867  0.1535275
[4,] -3.1169442  1.4892720  3.0819024  0.4171374
> 

18、基本的数据结构，数据框

> x1=c(10,13,45,26,23,12,24,78,23,43,31,56)
> x2=c(20,65,32,32,27,87,60,13,42,51,77,35)
> x=data.frame(x1,x2)
> x
   x1 x2
1  10 20
2  13 65
3  45 32
4  26 32
5  23 27
6  12 87
7  24 60
8  78 13
9  23 42
10 43 51
11 31 77
12 56 35
> 

> (x=data.frame('weight'=x1,'cost'=x2))
   weight cost
1      10   20
2      13   65
3      45   32
4      26   32
5      23   27
6      12   87
7      24   60
8      78   13
9      23   42
10     43   51
11     31   77
12     56   35
> 

19、读取文本文件、

> (x=data.frame('weight'=x1,'cost'=x2))
   weight cost
1      10   20
2      13   65
3      45   32
4      26   32
5      23   27
6      12   87
7      24   60
8      78   13
9      23   42
10     43   51
11     31   77
12     56   35
> (x=read.table("abc.txt"))
    V1 V2
1  175 67
2  183 75
3  165 56
4  145 45
5  178 67
6  187 90
7  156 43
8  176 58
9  173 60
10 170 56

20、读取excell文件

> w<-read.table("test.prn",header = T)
> w
  X.. X...1
1   A     2
2   B     3
3   C     5
4   D     5
> 

21、用readxl包读excell

> library(readxl)
> dat<-read_excel("test.xlsx")
> dat
# A tibble: 4 x 2
  `商品` `价格`
   <chr>  <dbl>
1      A      2
2      B      3
3      C      5
4      D      5
>