R

#####2.1.向量生成🌟#####

#(1)用 c() 结合到一起
c(2,5,6,2,9) 

## [1] 2 5 6 2 9

c("a","f","md","b")

## [1] "a"  "f"  "md" "b"

c(2,5,6,2,9,"a") 

## [1] "2" "5" "6" "2" "9" "a"

c("a","f","md","b")

## [1] "a"  "f"  "md" "b"

#(2)连续的数字用冒号“:” 
1:5

## [1] 1 2 3 4 5

#(3)有重复的用rep(),有规律的序列用seq(),随机数用rnorm()
rep("x",times = 3)  

## [1] "x" "x" "x"

seq(from = 3,to = 21,by = 3)

## [1]  3  6  9 12 15 18 21

rnorm(n = 3)

## [1] -1.8747110  0.6303876  0.2332628

#(4)通过组合,产生更为复杂的向量。
paste0(rep("x",times = 3),1:3)

## [1] "x1" "x2" "x3"

#####2.2对单个向量进行的操作####
#(1)赋值给一个变量名
x = c(1,3,5,1) #随意的写法
x

## [1] 1 3 5 1

x <- c(1,3,5,1) #规范的赋值符号 Alt+减号
x

## [1] 1 3 5 1

#赋值+输出一起实现
x <- c(1,3,5,1);x

## [1] 1 3 5 1

(x <- c(1,3,5,1))

## [1] 1 3 5 1

#(2)简单数学计算
x+1

## [1] 2 4 6 2

log(x)

## [1] 0.000000 1.098612 1.609438 0.000000

sqrt(x)

## [1] 1.000000 1.732051 2.236068 1.000000

#(3)根据某条件进行判断,生成逻辑型向量
x>3

## [1] FALSE FALSE  TRUE FALSE

x==3

## [1] FALSE  TRUE FALSE FALSE

#(4)初级统计
max(x) #最大值

## [1] 5

min(x) #最小值

## [1] 1

mean(x) #均值

## [1] 2.5

median(x) #中位数

## [1] 2

var(x) #方差

## [1] 3.666667

sd(x) #标准差

## [1] 1.914854

sum(x) #总和

## [1] 10

length(x) #长度

## [1] 4

unique(x) #去重复

## [1] 1 3 5

duplicated(x) #对应元素是否重复

## [1] FALSE FALSE FALSE  TRUE

table(x) #重复值统计

## x
## 1 3 5 
## 2 1 1

sort(x)

## [1] 1 1 3 5

sort(x,decreasing = F)

## [1] 1 1 3 5

sort(x,decreasing = T)

## [1] 5 3 1 1