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第二课

第二课
2023-06-13 09:18:17 时间

title: "向量的生成"

output: html_document

date: "2023-04-06"

小白的第二课

c(2,5,6,2,9)
## [1] 2 5 6 2 9
c("a","f","md","c")
## [1] "a"  "f"  "md" "c"
1:5
## [1] 1 2 3 4 5
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]  0.4295305 -0.9886426 -0.6427203
paste0(rep("x",times=3),1:3)
## [1] "x1" "x2" "x3"
x<-c(1,3,5,1)
x=c(1,3,5,1)
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
x>3
## [1] FALSE FALSE  TRUE FALSE
x==3
## [1] FALSE  TRUE FALSE FALSE
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
x = c(1,3,5,1)
y = c(3,2,5,6)
x == y 
## [1] FALSE FALSE  TRUE FALSE
y == x
## [1] FALSE FALSE  TRUE FALSE
x + y
## [1]  4  5 10  7
paste(x,y,sep=",")
## [1] "1,3" "3,2" "5,5" "1,6"
paste(x,y)
## [1] "1 3" "3 2" "5 5" "1 6"
#当两个向量长度不一致
x = c(1,3,5,6,2)
y = c(3,2,5)
x == y # 啊！warning！
## [1] FALSE FALSE  TRUE FALSE  TRUE
#循环补齐--看ppt
a = c(1,2)
b = c(1,2,3)
a+b
## [1] 2 4 4
a == b
## [1]  TRUE  TRUE FALSE
#利用循环补齐简化代码
paste0(rep("x",3),1:3)
## [1] "x1" "x2" "x3"
paste0("x",1:3)
## [1] "x1" "x2" "x3"
intersect(x,y)
## [1] 3 5 2
union(x,y)
## [1] 1 3 5 6 2
setdiff(x,y)
## [1] 1 6
setdiff(y,x)
## numeric(0)
x %in% y #x的每个元素在y中存在吗
## [1] FALSE  TRUE  TRUE FALSE  TRUE
y %in% x #y的每个元素在x中存在吗
## [1] TRUE TRUE TRUE
x <- 8:12
#根据逻辑值取子集
x[x == 10]
## [1] 10
x[x < 12]
## [1]  8  9 10 11
x[x %in% c(9,13)]
## [1] 9
#根据位置取子集
x[4]
## [1] 11
x[2:4]
## [1]  9 10 11
x[c(1,5)]
## [1]  8 12
x[-4]
## [1]  8  9 10 12
x[-(2:4)]
## [1]  8 12
####2.5.修改向量中的某个/某些元素：取子集+赋值
x
## [1]  8  9 10 11 12
#改一个元素
x[4] <- 40
x
## [1]  8  9 10 40 12
#改多个元素
x[c(1,5)] <- c(80,20)
x
## [1] 80  9 10 40 20
x[x%in%y]
## numeric(0)
#### 2.6 简单向量作图
k1 = rnorm(12);k1
##  [1]  0.4078494  1.8536021  0.6923547 -1.8542915 -1.2391541  0.5122553
##  [7] -1.1694122  0.7246900  0.3466781  0.2286454 -0.6850314 -0.4258046
k2 = rep(c("a","b","c","d"),each = 3);k2
##  [1] "a" "a" "a" "b" "b" "b" "c" "c" "c" "d" "d" "d"
plot(k1)
boxplot(k1~k2)

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