Hi,

Not exactly sure what you mean,  but try

? intersect

and see if this matches your need.

Cheers,
Umesh

On Sun, Mar 29, 2009 at 6:28 PM, Gabor Grothendieck <ggrothendieck@gmail.com
> wrote:

> Example 7c has been aded to the home page which illustrates how
> to do this using nested selects.
> http://sqldf.googlecode.com
>
> 2009/3/29 Schragi Schwartz <schragas@post.tau.ac.il>:
> > Hi,
> > Again, thank you for your extremely helpful answer. I'll try my luck a
> third
> > time with a similar but different question: assuming I have two
> dataframes,
> > a and b, each of which containing a set of start and end coordinates, and
> I
> > want to create a new dataframe c, which contains all coordinates in a
> which
> > are are overlapped by any coordinate in b. Can I do this via sqldf()? Or
> is
> > there any other way to do this?
> >
> > Thank you very much!
> > Schragi
> >
> > -----Original Message-----
> > From: Gabor Grothendieck [mailto:ggrothendieck@gmail.com]
> > Sent: Wednesday, March 25, 2009 3:44 PM
> > To: Schragi Schwartz
> > Cc: r-help@r-project.org
> > Subject: Re: [R] Merging rows in dataframes
> >
> > I've added an example to FAQ 3 on the home page that
> > illustrates group_concat.
> > http://sqldf.googlecode.com
> >
> > On Wed, Mar 25, 2009 at 9:06 AM, Gabor Grothendieck
> > <ggrothendieck@gmail.com> wrote:
> >> In the Links box to the right on the sqldf home page click on
> >> "SQLite - aggregate functions" and lookup group_concat.
> >>
> >> On Wed, Mar 25, 2009 at 9:05 AM, Schragi Schwartz
> >> <schragas@post.tau.ac.il> wrote:
> >>> Thank you, your answer was extremely helpful. One last problem though:
> > one
> >>> of the aggregate functions I'd like to apply on the columns is
> >>> concatentation (equivalent to the paste() function). So if I have a
> given
> >>> character column in three separate rows sharing the same ids with the
> > value
> >>> "apple" in the first, "banana" in the second, and "orange" in the
> third,
> > in
> >>> the summarizing row I'd like to receive output in the form
> >>> "apple|banana|orange". Is there any way to do this?
> >>>
> >>> Thanks again,
> >>> Schragi
> >>>
> >>> -----Original Message-----
> >>> From: Gabor Grothendieck [mailto:ggrothendieck@gmail.com]
> >>> Sent: Tuesday, March 24, 2009 12:50 AM
> >>> To: Schraga Schwartz
> >>> Cc: r-help@r-project.org
> >>> Subject: Re: [R] Merging rows in dataframes
> >>>
> >>> Using sqldf you only need two statements, infile <- file(...) and
> >>> DF <- sqldf("select min(a), max(b), mean(c), ... from infile group by
> > id").
> >>> The file statement identifies the filename and the second reads it
> >>> into sqlite (without
> >>> going through R), summarizes it and then reads the summarized version
> >>> into R.  You may also need to provide info on its format if its not in
> > the
> >>> default format.  See example 4a on home page and the other examples
> >>> there:
> >>> http://sqldf.googlecode.com
> >>>
> >>>
> >>> On Mon, Mar 23, 2009 at 5:58 PM, Schraga Schwartz
> >>> <schragas@post.tau.ac.il> wrote:
> >>>> Hello,
> >>>>
> >>>> I have a dataframe with 40 columns and around 450,000 rows. The first
> >>> column
> >>>> in each row is a factor id and the remaining are numeric. Some rows
> have
> >>> the
> >>>> same ids. What I want to do is to merge each set of rows sharing the
> > same
> >>>> ids (id set) into one single row (summarizing row) with that id. To
> > create
> >>>> the summarizing row, I'd like to apply a different function on each of
> > the
> >>>> original columns in the id set. Some columns within the summarizing
> row
> >>> will
> >>>> equal the mean of the columns in the id set, others will equal the
> >>> minimum,
> >>>> others the maximum.
> >>>>
> >>>> To do this, I tried using the by() function. However, this was
> extremely
> >>>> slow (it ran for more than two hours before I stopped it). Also, it
> used
> >>> up
> >>>> all of 16 GB of memory on my machine. Is there any more efficient
> >>> function,
> >>>> both in terms of time and memory, to do this sort of thing?
> >>>>
> >>>> Thank you very much,
> >>>> Schraga Schwartz
> >>>>
> >>>> ______________________________________________
> >>>> R-help@r-project.org mailing list
> >>>> https://stat.ethz.ch/mailman/listinfo/r-help
> >>>> PLEASE do read the posting guide
> >>> http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> >>>> and provide commented, minimal, self-contained, reproducible code.
> >>>>
> >>>
> >>>
> >>
> >
> >
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>

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