Thank you for clarifying, Dr. Gunter.  My bad.
Regards,
Jorge.-

On Thu, Oct 18, 2012 at 5:21 PM, Bert Gunter <gunter.berton@gene.com> wrote:

> No. You need to test more carefully.
>
> > a <- factor(c(1,3,5))
> > b <- factor(c(5,7))
> > c(a,b)
> [1] 1 2 3 1 2
> > lev <- sort(unique(f <- c(a,b)))
> > f <- factor(f,levels=lev)
> > f
> [1] 1 2 3 1 2
> Levels: 1 2 3
>
> ## but
>
> > unlist(list(a,b),use.names=FALSE)
> [1] 1 3 5 5 7
> Levels: 1 3 5 7
>
> However, Is level "5" in 'a' the same as level "5" in 'b' ? The OP
> fails to specify, and there's no reason to assume so.  So I would say
> clarification is required before any answer can be given.
>
> -- Bert
>
> On Wed, Oct 17, 2012 at 10:43 PM, Jorge I Velez
> <jorgeivanvelez@gmail.com> wrote:
> > Hi Sam,
> >
> > Perhaps the following?
> >
> >> a <- factor(5:1,levels=1:9)
> >> b <- factor(9:1,levels=1:9)
> >> lev <- sort(unique(f <- c(a, b)))
> >> f <- factor(f, levels = lev)
> >> str(f)
> >  Factor w/ 9 levels "1","2","3","4",..: 5 4 3 2 1 9 8 7 6 5 ...
> >
> > HTH,
> > Jorge.-
> >
> >
> > On Thu, Oct 18, 2012 at 3:44 PM, Sam Steingold <> wrote:
> >
> >> How do I concatenate two vectors of factors?
> >> --8<---------------cut here---------------start------------->8---
> >> > a <- factor(5:1,levels=1:9)
> >> > b <- factor(9:1,levels=1:9)
> >> > str(c(a,b))
> >>  int [1:14] 5 4 3 2 1 9 8 7 6 5 ...
> >> > str(unlist(list(a,b),use.names=FALSE))
> >>  Factor w/ 9 levels "1","2","3","4",..: 5 4 3 2 1 9 8 7 6 5 ...
> >> --8<---------------cut here---------------end--------------->8---
> >> so, unlist(list()) works.
> >> is there a better way or is this how this is supposed to be done?
> >> Thanks!
> >> --
> >> Sam Steingold (http://sds.podval.org/) on Ubuntu 12.04 (precise) X
> >> 11.0.11103000
> >> http://www.childpsy.net/ http://honestreporting.com
> >> http://think-israel.org http://thereligionofpeace.com
> >> http://mideasttruth.com
> >> (lisp programmers do it better)
> >>
> >> ______________________________________________
> >> 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.
> >>
> >
> >         [[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.
>
>
>
> --
>
> Bert Gunter
> Genentech Nonclinical Biostatistics
>
> Internal Contact Info:
> Phone: 467-7374
> Website:
>
> http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm
>

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