R devel - Jan 1998 - More on tapply and factors

Here is an even more awkward property of tapply with factors.  What we 
want to do is to determine the modal value of the first factor given
the level of the second factor.  We do that by applying table in a
tapply call then finding the maximum count then ...

Turns out that table gives unexpected results in tapply.
> table(Machines$Machine)
 A  B  C 
18 18 18 
> tapply( Machines$Machine, Machines$Worker, table )
$6
integer(0)

$2
integer(0)

$4
integer(0)

$1
integer(0)

$3
integer(0)

$5
integer(0)

-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To:
r-devel-request@stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._

Douglas Bates <bates@stat.wisc.edu> writes:
> > tapply( Machines$Machine, Machines$Worker, table )
> $6
> integer(0)
Yuk! Apparently, the culprit is "split":
> f1<-gl(2,1,4)
> f2<-gl(2,2,4)
> dput(split(f1,f2))
list(1 = factor(c(1, 2), levels=1:0), 2 = factor(c(1, 2), levels=1:0))
> dput(f1)
structure(factor(c(1, 2, 1, 2), levels=1:2), class = "factor", .Label
= c("1",
"2"))
> dput(f2)
structure(factor(c(1, 1, 2, 2), levels=1:2), class = "factor", .Label
= c("1",
"2"))

I wonder if this is a side effect of the ...hmm... "undesirable
feature" of as.numeric(factor)??

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907

-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To:
r-devel-request@stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._