[R] looking for a smarter way

[Cleland]

"Grum, Mikkel" wrote:

I have two problems where I've come up with some code that will do the 
analysis that I want, but it looks pretty clumsy.  In the first case, I 
calculate the variance on five different columns for each of 14 clusters
and get them into one matrix.  I get the job done, but I would have
thought that it could be done in one or two lines, not six, and be
generalized so that it didn't matter how many columns I had.  Any
suggestions?

  xtap1<-tapply(xcmd[,1],xclu$clustering,var)
  xtap2<-tapply(xcmd[,2],xclu$clustering,var)
  xtap3<-tapply(xcmd[,3],xclu$clustering,var)
  xtap4<-tapply(xcmd[,4],xclu$clustering,var)
  xtap5<-tapply(xcmd[,5],xclu$clustering,var)
  xtap<-cbind(xtap1,xtap2,xtap3,xtap4,xtap5)

Mikkel:

  I think you might be looking for something like this:

xtap <- apply(xcmd[,1:5], 2, function(x){tapply(x, list(xclu$clustering),
var)})

Hope this helps,

Chuck

-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-
Chuck Cleland
Institute for the Study of Child Development
UMDNJ--Robert Wood Johnson Medical School
97 Paterson St.
New Brunswick, NJ 08903
phone: (732) 235-7699
  fax: (732) 235-6189
http://www2.umdnj.edu/iscdweb/
http://members.nbci.com/cmcleland
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