[R] How to combine two data frames by ID

Christopher Desjardins
Wed, 15 Jul 2009 01:07:38 -0000

Hi,

I am trying to combine two data frames by ID. The first data frame is
the whole data set and the second data frame is a subset of the first.
What I would like to do is take the values from variable, p1, from the
second data frame and merge them back into that variable in the first
data frame. I have ID variables that match for both data frames and the
data frames obviously have differing number of rows where the first data
frame > second data frame. I want to keep the pre existing data for this
variable that is present in the first data frame and only write over the
data that I edited in the second.

Thanks and please cc me as I am a digest subscriber,
Chris