R help - Aug 2008 - Interaction between aggregate() and length()

Folks,

I've been running into an odd situation that occurs when I use length() 
function with aggregate(), but not with either one separately.  Together, 
the results looks correct but is given an unexpected name. 'if 
(stringsAsFactors) factor(x) else x' instead of just 'x'.

# Numbers work ok
tt <- data.frame(idx=c(1,1,1,1,1,1,2,2,2,2,2,2)
                ,n=c(1,3,5,7,5,5,2,4,8,16,4,4)
                ,t=c(1,3,5,7,5,5,2,4,8,16,4,4)
                ,stringsAsFactors=FALSE)

aggregate(tt$t, list('idx'=tt$idx), length)
aggregate(as.factor(tt$t), list('idx'=tt$idx), length)

# Character data doesn't work right unless I convert the data to factors.
tt <- data.frame(idx=c(1,1,1,1,1,1,2,2,2,2,2,2)
               
,n=c('1','3','5','7','5','5','2','4','8','16','4','4')
               
,t=c('1','3','5','7','5','5','2','4','8','16','4','4')
                ,stringsAsFactors=FALSE)

aggregate(tt$t, list('idx'=tt$idx), length)
aggregate(as.factor(tt$t), list('idx'=tt$idx), length)


Any idea what is going on here?  For the record, this also happens with 
the modalvalue() function defined at 
http://wiki.r-project.org/rwiki/doku.php?id=tips:stats-basic:modalvalue 
(which also relies on length() ).

As a side note, this began as an attempt to determine sample size, for 
which I've defined a function count <- function(x) { length(na.omit(x))
}.
 No doubt there's a built in function to do just that, but as a newbie 
I've yet to find it.

Thank you for your help,
cur
-- 
Curt Seeliger, Data Ranger
Raytheon Information Services - Contractor to ORD
seeliger.curt@epa.gov
541/754-4638

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One option is use this:

aggregate(list(t=tt$t), list(idx=tt$idx), length)

On Thu, Aug 28, 2008 at 4:36 PM, <Seeliger.Curt@epamail.epa.gov> wrote:
> Folks,
>
> I've been running into an odd situation that occurs when I use length()
> function with aggregate(), but not with either one separately.  Together,
> the results looks correct but is given an unexpected name. 'if
> (stringsAsFactors) factor(x) else x' instead of just 'x'.
>
> # Numbers work ok
> tt <- data.frame(idx=c(1,1,1,1,1,1,2,2,2,2,2,2)
>                ,n=c(1,3,5,7,5,5,2,4,8,16,4,4)
>                ,t=c(1,3,5,7,5,5,2,4,8,16,4,4)
>                ,stringsAsFactors=FALSE)
>
> aggregate(tt$t, list('idx'=tt$idx), length)
> aggregate(as.factor(tt$t), list('idx'=tt$idx), length)
>
> # Character data doesn't work right unless I convert the data to
factors.
> tt <- data.frame(idx=c(1,1,1,1,1,1,2,2,2,2,2,2)
>               
,n=c('1','3','5','7','5','5','2','4','8','16','4','4')
>               
,t=c('1','3','5','7','5','5','2','4','8','16','4','4')
>                ,stringsAsFactors=FALSE)
>
> aggregate(tt$t, list('idx'=tt$idx), length)
> aggregate(as.factor(tt$t), list('idx'=tt$idx), length)
>
>
> Any idea what is going on here?  For the record, this also happens with
> the modalvalue() function defined at
> http://wiki.r-project.org/rwiki/doku.php?id=tips:stats-basic:modalvalue
> (which also relies on length() ).
>
> As a side note, this began as an attempt to determine sample size, for
> which I've defined a function count <- function(x) {
length(na.omit(x)) }.
>  No doubt there's a built in function to do just that, but as a newbie
> I've yet to find it.
>
> Thank you for your help,
> cur
> --
> Curt Seeliger, Data Ranger
> Raytheon Information Services - Contractor to ORD
> seeliger.curt@epa.gov
> 541/754-4638
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> 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
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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