[R] Simple Merge

[Jeff]

I'm new to R.

I have two data frames I need to merge. One has an ID column the 
other does not, but both have the same number of rows that are 
ordered in the same way - e.g., row 1 is the same person in both data 
frames. For this reason, there is no need to sort or specify a "by" column.

I can't seem to figure out how to do this from anything I can find on-line.

Can someone point me in the right direction ?

Thanks

Jeff