[R] Using nrow with summaryBy

[Gabor Grothendieck]

Use NROW rather than nrow.

On Wed, Mar 17, 2010 at 11:23 AM, Tony Laidig <c64 at mit.edu> wrote:
> Hello Everyone-
> I'm calculating summary statistics on a dataset (~4000 records,
> observations are not uniformly distributed) using summaryBy and trying
> to add a column with the number of observations to the output as well.
> What occurs to me is to use nrow(), but this doesn't appear to be working
>
> I'm able to replicate the same results with an example from the
> summaryBy docs:
>
> data(dietox)
> dietox12<- subset(dietox,Time==12)
> library(doBy)
> #this one works
> summaryBy(Weight+Feed~Evit+Cu,data=dietox12,FUN=c(mean,var,length))
> #adding nrow doesn't give the number of rows
> summaryBy(Weight+Feed~Evit+Cu,data=dietox12,FUN=c(mean,var,length,nrow))
>
>
> There must be a way to do this, but I can't figure it out. I suspect
> there is another function that would be compatible with summaryBy.
>
> Thanks in advance.
> -Tony
>
>
>
>
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