R help - Feb 2006 - (Newbie) Merging two data frames

This one is an easy question. I am looking for the "idiomatic" way to
do it.

I have two large data frames. I want to "merge" them. What is the
idiomatic way to say "match the rows from dataframe 1 to the rows in
dataframe2 which have the following fields the same: Identifier, Year
and Quarter? (These three fields form something like a composite
primary key in SQL). Then tell me which rows you could not find a
match for.... etc.

-- Vivek Satsangi
Student, Rochester, NY USA

On Wed, 2006-02-01 at 17:10 -0500, Vivek Satsangi wrote:
> This one is an easy question. I am looking for the "idiomatic"
way to do it.
> 
> I have two large data frames. I want to "merge" them. What is the
> idiomatic way to say "match the rows from dataframe 1 to the rows in
> dataframe2 which have the following fields the same: Identifier, Year
> and Quarter? (These three fields form something like a composite
> primary key in SQL). Then tell me which rows you could not find a
> match for.... etc.

You answered your own question...  :-)

See ?merge

which will perform SQL-like joins.

HTH,

Marc Schwartz