?merge says
Merge two data frames by common columns or row names, or do other
versions of database ``join'' operations.
and it has done all the examples of this sort of thing that I have ever
needed.
On 24 Jun 2003, Douglas Bates wrote:
> In our recent workshop on "Multilevel Modeling in R" we discussed
> handling data for multilevel modeling. An classic example of such
> data are test scores of students grouped into schools. We may wish to
> model the scores as functions of both student-level covariates and
> school-level covariates.
>
> Such data are often organized in a multi-table format with a separate table
> for each level of information. The MathAchieve and MathAchSchool data
> frames in the nlme package are examples of such an organization. The
> HLM software requires the data to be organized like this. To fit a
> model in R we need to create a composite table by "joining" the
> columns of the student-level and school-level tables, in the
> relational database sense of "join".
>
> I have created a function to join the columns from two such frames
> according to the values of a key column. In relational database terms
> the key column must be a primary key for the second frame. I have
> called this function 'cjoin', by analogy to cbind.
>
> You can try
>
> data(MathAchieve, package = 'nlme')
> data(MathAchSchool, package = 'nlme')
> cjoin(MathAchieve, MathAchSchool, "School")
> cjoin(MathAchieve, MathAchSchool, "School", which = "Sector")
>
> as examples
>
> Several questions:
>
> - Am I duplicating existing functionality?
>
> - Is cjoin a good name for such a function?
>
> - Would this be useful in base?
>
>
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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