Re: [R] Summarize by two-column factor, retaining original factors

From: Gabor Grothendieck <ggrothendieck_at_gmail.com>
Date: Sat 25 Feb 2006 - 03:34:03 EST

Or even

aggregate(DF[3:4], DF[1:2], sum)

On 2/24/06, Marc Schwartz (via MN) <mschwartz@mn.rr.com> wrote:
> On Fri, 2006-02-24 at 08:18 -0800, Matt Crawford wrote:
> > I am having trouble doing the following. I have a data.frame like
> > this, where x and y are a variable that I want to do calculations on:
> >
> > Name Year x y
> > ab 2001 15 3
> > ab 2001 10 2
> > ab 2002 12 8
> > ab 2003 7 10
> > dv 2002 10 15
> > dv 2002 3 2
> > dv 2003 1 15
> >
> > Before I do all the other things I need to do with this data, I need
> > to summarize or collapse the data by name and year. I've found that I
> > can do things like
> > nameyear<-interaction(name,year)
> > dataframe$nameyear<-nameyear
> > tapply(dataframe$x,dataframe$nameyear,sum)
> > tapply(dataframe$y,dataframe$nameyear,sum)
> > and then bind those together.
> >
> > But my problem is that I need to somehow retain the original Names in
> > my collapsed dataset, so that later I can do analyses with the Name
> > factors. All I can think of is something like
> > tapply(dataframe$Name,dataframe$nameyear, somefunction?)
> > but nothing seems to work.
> >
> > I'm actually trying to convert a SAS program, and I can't get out of
> > that mindset. There, it's a simple Proc Means, By Name Year.
> >
> > Thanks for any help or suggestions on the right way to go about this.

> >
> > Matt Crawford
>
> Matt,
>
> Just use aggregate():
>
> > aggregate(MyDF[, 3:4], list(Name = MyDF$Name, Year = MyDF$Year), sum)
> Name Year x y
> 1 ab 2001 25 5
> 2 ab 2002 12 8
> 3 dv 2002 13 17
> 4 ab 2003 7 10
> 5 dv 2003 1 15
>
>
> See ?aggregate for more information.
>
> HTH,
>
> Marc Schwartz
>
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R-help@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 Received on Sat Feb 25 03:43:55 2006

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