[R] REmove level with zero observations

[Bert Gunter]

Actually, you probably want to remove the remaining level -- that is,
remove the variable altogether, since if it has only a single value
its effect is indistinguishable from the overall mean.

Again, complying with the posting guide would be advisable.

Bert Gunter
Genentech Nonclinical Biostatistics



On Tue, Aug 3, 2010 at 1:50 PM, GL <pflugg at shands.ufl.edu> wrote:
>
> If I have a column with 2 levels, but one level has no remaining
> observations. Can I remove the level?
>
> Had intended to do it as listed below, but soon realized that even though
> there are no observations, the level is still there.
>
> For instance
>
> summary(dbs3.train.sans.influential.obs$HAC)
>
> yields
>
> 0 ,1
> 4685,0
>
> nlevels(dbs3.train.sans.influential.obs$HAC)
>
> yields
> [1] 2
>
> drop.list <- NULL
> for (i in 1:ncol(dbs3.train.sans.influential.obs)) {
>     if (nlevels(dbs3.train.sans.influential.obs[,i]) < 2) {drop.list <-
> cbind(drop.list,i)}}
>
> yields
> nothing because HAC still has two levels, even though there aren't any
> observations in on of the levels.
>
> What I want to do is loop through all columns that are factors and create a
> list of items to drop because there will subsequently be < 2 levels when I
> try to run a linear model.
>
>
> --
> View this message in context: http://r.789695.n4.nabble.com/REmove-level-with-zero-observations-tp2312553p2312553.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at 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.
>