R語言之書2.3.3
- 2019 年 12 月 31 日
- 筆記
#章節1 新手入門
getwd()
setwd("D:/R")
setwd("D:R")
library("MASS")
?mean
??"mean"
?mean
q()
#章節2.1基礎數學
sqrt(x=9) #計算非負值的平方根
2^(2+1)-4+64^((-2)^(2.25-1/4)) #-2要加括弧
log(x=243,base=3) #對數
exp(x=3) #指數
#練習
(6*2.3+42)/(3^(4.2-3.62))
sqrt((mean(25.2,12,16.44,15.3,18.6))/2)
log(x=0.3,base=exp(1)) #exp(1)=e=2.718
-0.00000000423546322 #-4.235463e-09
exp(log(x=0.3,base=exp(1)))
#章節2.2分配對象
x<–5
x=x+1
mynumber=45.2
y<-mynumbe
ls() #查看當前工作空間所包含的內容
#練習
x<-(3^2)*(4^(1/8))
x<-x/2.33
y<–8.2*(10^(-13))
x*y
#章節2.3向量
myvec<-c(1,3,1,42) #創建向量
myvec
foo<-32.1
myvec2<-c(3,-3,2,3,45,1e+03,64^0.5,2+(3-1)/9.44,foo)
myvec2
myvec3<-c(myvec,myvec2)
myvec3
#序列
3:27 #從3開始逐項加1到27為止
foo<-5.3
bar<-foo:(-47+1.5) #從5.3開始逐項減1
ba
seq(from=3,to=27,by=3) #序列函數seq
seq(from=3,to=27,length.out=40) #40個等間隔的數
myseq<-seq(from=foo,to=(-47+1.5),by=-2.4) #遞減序列
myseq
myseq2<-seq(from=foo,to=(-47+1.5),length.out=5)
myseq2
rep(x=1,times=4) #重複函數rep
rep(x=c(3,62,8.3),times=3) #times的值為重複x的次數
rep(x=c(3,62,8.3),each=2) #each的值為重複元素的個數
rep(x=c(3,62,8.3),times=3,each=2)
foo<-4
c(3,8.3,rep(x=32,times=foo),seq(from=-2,to=1,length.out=foo+1))
sort(x=c(2.5,-1,-10,3.44),decreasing=FALSE) #排序函數sort
sort(x=c(2.5,-1,-10,3.44),decreasing=TRUE)
foo<-seq(from=4.3,to=5.5,length.out=8)
foo
bar<-sort(x=foo,decreasing=TRUE)
ba
sort(x=c(foo,bar),decreasing=FALSE)
length(x=c(3,2,8,1)) #長度函數length
length(x=5:13)
foo<-4
bar<-c(3,8.3,rep(x=32,times=foo),seq(from=-2,to=1,length.out=foo+1))
length(x=bar)
#練習
x<-seq(from=5,to=-11,by=-0.3)
x
x<-sort(x,decreasing=FALSE)
x
x2<-sort(rep(x=c(-1,3,-5,7,-9),times=2,each=10),decreasing=FALSE)
x2
length(x2)
x<-seq(from=6,to=12)
y<-rep(x=5.3,times=3)
z<-c(seq(from=6,to=12),rep(x=5.3,times=3),-3,seq(from=102,to=100,length.out=9))
length(z)
#2.3.3子集和元素的提取
myvec<-c(5,-2.3,4,4,4,6,8,10,40221,-8)
length(myvec)
myvec[1]
foo<-myvec[2]
foo
myvec[length(x=myvec)]
myvec.len<-length(x=myvec)
bar<-myvec[myvec.len-1]
ba
1:myvec.len
myvec[-1]
baz<-myvec[-2]
baz
qux<-myvec[-(myvec.len-1)]
qux
c(qux[-length(x=qux)],bar,qux[length(x=qux)])
length(x=qux)
qux[-length(x=qux)]
bar<-myvec[myvec.len-1]
ba
qux[length(x=qux)]
myvec[c(1,3,5)]
1:4
foo<-myvec[1:4]
foo
length(x=foo):2
foo[length(foo):2]
indexes<-c(4,rep(x=2,times=3),1,1,2,3:1)
indexes
foo[indexes]
bar<-c(3,2,4,4,1,2,4,1,0,0,5)
ba
bar[1]<-6
ba
bar[c(2,4,6)]<-c(-2,-0.5,-1) #用向量替換多個元素的值
ba
bar[7:10]<-100
ba
#練習
x<-seq(from=3,to=6,length.out=5)
x
y<-rep(x=c(2,-5.1,-33),times=2)
y
z<-7/42+2
z
x<-c(x,y,z)
x
x1<-x[c(1,5)]
x3<-x[-c(1,5)]
x4<-c(x1,x3)
sort(x=x,decreasing=FALSE)
x5<-sort(x=x,decreasing=FALSE)
x6<-x5[5:1] #使用冒號作為索引顛倒順序
x6
x7<-c(rep(x=x3[4],times=3),rep(x=x3[6],times=4),rep(x=x3[10],times=1))
x7
x8<-sort(x=x,decreasing=FALSE)
x8[c(1,5:7,12)]<-c(99:95)
x8
