[R] adding variables to a data set/combining two data sets

[Marc Schwartz]

On Wed, 2005-11-23 at 16:13 -0700, nhepburn wrote:
> I have a couple of data sets that I want to combine into one data frame.
> One set contains a number of records on individual observations and includes
> a geographic descriptor called dacode.  The dacode is not unique in that
> table.  The other table contains a number of socio-economic variables for
> each of the geographic areas identified in the other table.  This second
> table also includes a variable called dacode and I have also used dacode for
> the rownames.  I want to pull a number of the variables from the
> socioeconomic status data into the first table but I'm having no luck.
> Here's what I have tried so far:
>  
> #first attempt
>  
> grade6DA$ses1 <- sesdata$ses1[as.character(grade6DA$dacode)]
>  
> All that this does is create a new column in the grade6DA data set and calls
> it ses1 but then fills it with NA.
>  
> 
> #second attempt
> grade6DA$ses1 <- sesdata$ses1[grade6DA$dacode]
>  
> 
> Neither approach has worked so I've ended up combining the tables in a MySQL
> database and then importing back into R.  However, it would be much easier
> if I could just manipulate the variables in R rather than going through
> MySQL everytime I want to try something new.  I've looked in the R-manuals
> but did not see anything about this - but I could have been looking in the
> wrong places.  Any ideas on how to accomplish what I am trying to do or
> advice on where to find the info would be greatly appreciated.
>  
> Cheers,
> Neil

Neil,

See ?merge which performs a SQL join type operation.

HTH,

Marc Schwartz

P.S. To R Core: help.search("join") does not seem to return merge(),
which would likely be helpful here.