Hello -
David Kaplan wrote:
Greetings all,
I have three files that I would like to merge. The first is a student
level file that contains the student ID, their school ID, and their
country ID.
The second is the school file that contains the school ID and country ID.
The third is the country file with a country ID.
I would like to merge the three together using the common country ID.
Of course, what this would mean is that school data be repeated for
every student in their school, and country data repeated for every
school and student in that country.
Any direction would be helpful.
I believe what you are after is to use the merge function. 'merge'
takes two data.frames, so to merge 3 data.frames, you'll have to use it
twice. You may want the all = TRUE argument to merge also.
Example, with your data.frames, it might look like:
tmp <- merge(student, school, all = TRUE)
df <- merge(tmp, country, all = TRUE)
One thing to watch out for is that the merge function will merge on the
common names in each data.frame, in your case country ID. Sometimes I
check before the merge what variables it will attempt to merge on by using
intersect(names(student), names(school))
and making sure it is what I expect, i.e. ususally only one common name.
Hope that helps.
Thanks in advance,
David
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