[R] R is not for Relational

Russell Senior seniorr at teleport.com
Tue Aug 3 22:10:50 CEST 1999

>>>>> "Peter" == Peter Dalgaard BSA <p.dalgaard at biostat.ku.dk> writes:

John> R is not for Relational, but could be...

John> I was musing on data.frames when I decided what I needed was a
John> SQL like 'select' statement.

John> Before I get involved in writing something like that, has anyone
John> else written anything that allows a relational like algebra on
John> data.frames?

Peter> Check if subset() does something in the right direction. What
Peter> would the select statement do, precisely? (I don't speak SQL)

One useful thing that subset() doesn't appear to do is joins.  That is
frequently what select statements are used for in SQL.  There are
three S-plus functions (at least, as documented in MASS 2ed) called
merge, by and aggregate.  The merge() function joins data frames, but
is not implemented in R that I am aware of, at least as of 0.64.0.

Russell Senior         ``The two chiefs turned to each other.        
seniorr at teleport.com     Bellison uncorked a flood of horrible       
                         profanity, which, translated meant, `This is
                         extremely unusual.' ''                      
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