I think this will work. Thanks. But, is there a command to merge on a
string variable. All I have is the country 3 letter designation.
Thanks again,
David
=======================================================================
David Kaplan, Ph.D.
Professor
Department of Educational Psychology
University of Wisconsin - Madison
Educational Sciences, Room, 1061
1025 W. Johnson Street
Madison, WI 53706
email: [EMAIL PROTECTED]
homepage:
http://www.education.wisc.edu/edpsych/default.aspx?content=kaplan.html
Phone: 608-262-0836
=======================================================================
Erik Iverson wrote:
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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