David:
Is this what you are looking for?
set.seed(10)
tmp <- data.frame(group = gl(3,10), something = rnorm(30))
with(tmp, tapply(something, group, mean))
1 2 3
-0.4906568 0.3695915 -0.9129640
> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of David Kaplan
> Sent: Wednesday, November 29, 2006 2:16 PM
> To: Chuck Cleland; r-help at stat.math.ethz.ch
> Subject: Re: [R] Aggregating data
>
> Chuck and others. Here is the problem I need help on. Thanks.
>
> --------------------
>
> I want to follow-up on a question I had a week or so ago. I
> want to aggregate a very large data set. Generally in a
> program such as SPSS, one chooses a so-called "break
> variable" that is the variable, and then the remaining
> variables are aggregated by that variable with some summary
> statistic calculated - such as the mean.
>
> I played with "aggregate" in R and found that it requires a
"by"
> statement listing the variables. But I don't see how I can
> aggregate on one variable and create the summary statistics
> on the remaining variables. I hope that was clear. Thanks
> for an advice in advance.
>
> David
> =============================================================>
============> David Kaplan, Ph.D.
> Professor
> Department of Educational Psychology
> University of Wisconsin - Madison
> Educational Sciences, Room, 1061
> 1025 W. Johnson Street
> Madison, WI 53706
>
> email: dkaplan at education.wisc.edu
> homepage:
> http://www.education.wisc.edu/edpsych/facstaff/kaplan/kaplan.htm
> Phone: 608-262-0836
> =============================================================>
============>
> Chuck Cleland wrote:
> > David Kaplan wrote:
> >> The problem is that this doesn't seem to give what I want. I
did
> >> look at this. Perhaps doBy will work - haven't tried it
> yet. But,
> >> any other suggestions are much appreciated.
> >
> > David:
> > Your posts on aggregating came to the list without any
> text in the
> > body of the message (I believe Petr sent a response based
> only on the
> > subject). You might get more specific and helpful
> suggestions if you
> > send a small example of what you are trying to do and why
> aggregate()
> > does not work for you. Also, be sure to send messages in
> plain text
> > rather than HTML.
> >
> > hope this helps,
> >
> > Chuck Cleland
> >
> >>
> ====================================================================>
>> =====> >> David Kaplan, Ph.D.
> >> Professor
> >> Department of Educational Psychology
> >> University of Wisconsin - Madison
> >> Educational Sciences, Room, 1061
> >> 1025 W. Johnson Street
> >> Madison, WI 53706
> >>
> >> email: dkaplan at education.wisc.edu
> >> homepage:
> >> http://www.education.wisc.edu/edpsych/facstaff/kaplan/kaplan.htm
> >> Phone: 608-262-0836
> >>
> ====================================================================>
>> =====> >>
> >> Petr Pikal wrote:
> >>> Similar answer as last time
> >>>
> >>> aggregate, tapply, by or ppackage doBy
> >>>
> >>> HTH
> >>>
> >>> PS. If you want to add some other text then subject in
> your post do
> >>> not use HTML posting as recommended in posting guide.
> >>>
> >>> Petr
> >>>
> >>>
> >>> On 28 Nov 2006 at 22:04, David Kaplan wrote:
> >>>
> >>> Date sent: Tue, 28 Nov 2006 22:04:09 -0600
> >>> From: David Kaplan <dkaplan at
education.wisc.edu>
> >>> To: r-help at stat.math.ethz.ch
> >>> Subject: [R] Aggregating data
> >>>
> >>>> ______________________________________________
> >>>> R-help at stat.math.ethz.ch mailing list
> >>>> https://stat.ethz.ch/mailman/listinfo/r-help
> >>>> PLEASE do read the posting guide
> >>>> http://www.R-project.org/posting-guide.html and provide
> commented,
> >>>> minimal, self-contained, reproducible code.
> >>> Petr Pikal
> >>> petr.pikal at precheza.cz
> >>>
> >> ______________________________________________
> >> R-help at stat.math.ethz.ch mailing list
> >> https://stat.ethz.ch/mailman/listinfo/r-help
> >> PLEASE do read the posting guide
> >> http://www.R-project.org/posting-guide.html
> >> and provide commented, minimal, self-contained, reproducible code.
> >>
> >
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>