How can I inner join two csv files in R?

I have two csv files.

File one has two columns:

DD1 abct
DD2 geate
DD3 watec
DD4 wwwca21
DD5 bate789

File two has one column:

abct
geate
bate789

I want to get a truncated file one to include those that matched with file two, i.e.

DD1 abct
D开发者_如何学GoD2 geate
DD5 bate789

Could you mind to let me know how to do it with R?

New to R.

First, read the files with the read.table:

file1 <- read.table("file1.csv", col.names=c("FOO", "BAR"))
file2 <- read.table("file2.csv", col.names=c("BAR"))

Then merge them:

merged <- merge(file1, file2)

And write the result:

write.table(merged, "merged.csv")

This is a direct way to do it by doing %in%. This will be about the fastest way entirely within R.

read in the files

datf1 <- read.table("file1.csv") #two column file
datf2 <- read.table("file2.csv") #one column file

select the rows you want... %in% makes a logical vector that is the length of the first argument and is TRUE when an item is in both of the arguments and FALSE otherwise.

datf1 <- datf1[datf1[,2] %in% datf2[,1],]

write it out... I changed the file name from file1 because you really shouldn't overwrite your original data and make a new file1.

write.table(datf1, "file3.csv", sep = ',', row.names = FALSE, quote = FALSE)