[R] data frames; matching/merging

S Ellison S.Ellison at lgc.co.uk
Mon Feb 8 17:59:16 CET 2010

You could try aggregate:

If we call your data frame df:

aggregate(df[2], by=df[1], FUN=min)

will get you what you asked for (if not necessarily what you need ;-)

Switching the columns around is easy enough if you need to; proceeding
df.new<-aggregate(df[2], by=df[1], FUN=min)

As to how I found aggregate: watching R-help daily for years
occasionally pops up fundamental gems like aggregate...

 Steve Ellison

>>> Jonathan <jonsleepy at gmail.com> 08/02/2010 16:39:11 >>>
What I'd like is to return a dataframe cut down to have only unique
entires in V1.  V2 should contain a vector, for each V1, that is the
minimum of all the possible choices from the set of redundant V1's.

Example output:

      V1     V2
1     a        2
2     b        9
3     c        4

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