install.packages("readxl")
getwd()
setwd("E:/作業4")
library(readxl) tianmao<-read_excel('tianmaoTV.xlsx',skip=1)#把第一行跳過，直接從第二行開始讀取
#創建新變量
tianmao['total_sales']<-tianmao$current_price*tianmao$month_sales_count
tianmao[c('current_price','month_sales_count','total_sales')]tianmao$zhekou<-tianmao$current_price/tianmao$original_price
tianmao$zhekoua<-1:10
ifelse(a%%2==0,'偶數', '奇數')tianmao['price_class']<-ifelse(tianmao$current_price<1000,'低價',ifelse(tianmao$current_price<=2000,"適中",'高價'))
tianmao[c('price_class','current_price')]#重命名
names(tianmao)
names(tianmao)[1]<-'mingcheng'%in% #判斷符號前的向量的元素是否是在符號后面的向量中，返回邏輯向量，如果在后面向量中，就返回true
names(tianmao)%in%"weight" #是true的就說明這個元素在weight里面
names(tianmao)[names(tianmao)%in%"weight"]
names(tianmao)[names(tianmao)%in%"weight"]<-'zhongliang'
names(tianmao)#提取子集
newdata<-tianmao[,-c(1:3)]
names(newdata)
names(tianmao)col1<-c('mingcheng','description','current_price')
logical<-names(tianmao)%in%col1
newdata1<-tianmao[,!logical]
names(newdata1)tianmao[1,]
logical1<-tianmao$brand=='Xiaomi/小米'
xiaomi<-tianmao[logical1,]
xiaomi?subset
xiaomi1<-subset(tianmao,brand=='Xiaomi/小米',c("mingcheng","description"))#homework Q1
library(readxl)
tianmao_2 <- read_excel("E:/作業4/tianmaoTV.xlsx",skip = 1)
View(tianmao_2)#homewotk Q2
logical<-tianmao_2$current_price<1000
tianmao_Q2<-tianmao_2[logical,]
View(tianmao_Q2)#homework Q3
tianmao_2$stock_class<-ifelse(tianmao_2$stock==0,'無貨',ifelse(tianmao_2$stock<100,'低庫存','高庫存'))
View(tianmao_2)#homework Q4
tianmao_Q4<-tianmao_2[c('stock','stock_class')]
tianmao_Q4#homewotk Q5
names(tianmao_2)
tianmao_Q5<-tianmao_2[,-c(7,8)]
names(tianmao_Q5)

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