Thank you Michael,

However, this only provides the number of groups without a column label.
Is there a way to have it give the count with the 'ID' label?

Regards,
Charles

On Fri, May 25, 2012 at 10:52 AM, R. Michael Weylandt <
michael.weylandt@gmail.com> wrote:

> length(unique(ID))
>
> Michael
>
> On Fri, May 25, 2012 at 11:38 AM, Charles Determan Jr <deter088@umn.edu>
> wrote:
> > Hello,
> >
> > Simple question that I am stuck on and can't seem to find an answer in
> the
> > help files currently.  I have a list which contains repeated ID's.  I
> would
> > like to have R count the number of ID's.  For example:
> >
> > ID=c(1,1,1,1,2,2,2,2,3,3,3,3)
> > as.data.frame(ID)
> >
> > Clearly, there are 3 groups.  How would I have R give me the summary:
> >
> > ID
> > 3
> >
> > Many thanks,
> > Charles
> >
> >        [[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.
>

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