完全小白，求指导
以下是从头开始的命令
setwd("D:/R")
getwd()

df1<-read.csv("ChinaA.csv",header = T)
df2<-read.csv("USA.csv",header = T)
df3<-read.csv("Germany.csv",header = T)
df4<-read.csv("Japan.csv",header = T)
df5<-read.csv("UK.csv",header = T)
head(df1)
tail(df1)
colnames(df1)<-c("date","y")
colnames(df2)<-c("date","x1")
colnames(df3)<-c("date","x2")
colnames(df4)<-c("date","x3")
colnames(df5)<-c("date","x4")

df1$date<-as.Date(df1$date)
df2$date<-as.Date(df2$date)
df3$date<-as.Date(df3$date)
df4$date<-as.Date(df4$date)
df5$date<-as.Date(df5$date)
head(df1)
tail(df1)

merged<-merge(df1,df2,by="date",all=T)
head(merged)
tail(merged)
merged<-merge(merged,df3,by="date",all=T)
head(merged)
tail(merged)
merged<-merge(merged,df4,by="date",all=T)
head(merged)
tail(merged)
merged<-merge(merged,df5,by="date",all=T)
head(merged)
tail(merged)
merged

merged_new<-na.omit(merged)
dim(merged_new)
head(merged_new)
tail(merged_new)

install.packages ("dplyr")
setwd("C:/Users/徐/AppData/Local/Temp/Rtmp2V0bsM/downloaded_packages")
library(dplyr)
merged_new <- select(merged_new,-date)
merged_new
setwd("D:/R")
write.csv(merged_new,file = "merged.csv",row.names = F)

getwd()
z<-read.csv("D:/R/merged.csv")

z
tail(z)
colnames(z)<-c("y","x1","x2","x3","x4")
dim(y)
print(as.numeric(y))