How to merge 2 files with R

dat <- read.table("PLMLMeditGenepop.txt")

head(dat)

dat2 <- read.table("CoordMedit.txt")

head(dat2)

# Fusion des tables

dfr2 <- cbind.data.frame(dat2, dat)

head(dfr2)

write.table(dfr, "LnPD.txt", sep=" ", row.names=F, quote=F)

# Classer par longitude

dfr3<-dfr2[ order(dfr2$V2), ]

head(dfr3)

dfr4 <- dfr3[,-1:-2]

dfr4

write.table(dfr4, "genpopMeditFinal.txt", sep=" ", row.names=F, quote=F)

dfr5 <- dfr4[,!colnames(dfr4)=="nb"]

head(dfr5)

dat <- read.table("table.txt")

head(dat)

write.table(dat, "table.csv", sep=";", row.names=F, quote=F)