[R] Keeping factors with zero occurrences in "table" output

[Ravi Varadhan]

Thanks very much to Achim Zeileis, Matt Weiner, and Andy Liaw for their
solution.  Declaring preferences as a "factor" worked!

Best,
Ravi.

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Ravi Varadhan, Ph.D.
Assistant Professor,  The Center on Aging and Health
Division of Geriatric Medicine and Gerontology
Johns Hopkins University
Ph: (410) 502-2619
Fax: (410) 614-9625
Email:  rvaradhan at jhmi.edu
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> -----Original Message-----
> From: Achim Zeileis [mailto:Achim.Zeileis at wu-wien.ac.at]
> Sent: Wednesday, April 20, 2005 12:13 PM
> To: Ravi Varadhan
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] Keeping factors with zero occurrences in "table" output
> 
> On Wed, 20 Apr 2005 11:38:13 -0400 Ravi Varadhan wrote:
> 
> > Dear R group,
> >
> >
> >
> > I have a data frame which contains data on preferences on 7 items
> > (ranks 1 through 7) listed by each participant.  I would like to
> > tabulate this in a 7x7 table where the rows would be the items and the
> > columns would be the number of times that item received a particular
> > rank.
> >
> > I tried doing this by creating a matrix by "rbind"ing each vector
> > obtained using "table" on each item.  This, however, does not work
> > because there are some items which didn't receive some of the ranks,
> > so "table" does not list that item.  Is there a way to force it to
> > list the item and give a "0" to it? Or, is there a simpler way to
> > solve this problem?
> 
> I think the cleanest way is to store the preferences as a "factor" and
> tell R at the creation of that factor what the levels are, i.e.
>   preference <- factor(preference, levels = 1:7)
> Then calling
>   table(preference)
> will also report categories with 0 observations.
> Z
> 
> 
> >
> >
> > Thanks for any help,
> >
> > Ravi.
> >
> >
> >
> > ---------------------------------------------------------------------
> > -----
> >
> > Ravi Varadhan, Ph.D.
> >
> > Assistant Professor,  The Center on Aging and Health
> >
> > Division of Geriatric Medicine and Gerontology
> >
> > Johns Hopkins University
> >
> > Ph: (410) 502-2619
> >
> > Fax: (410) 614-9625
> >
> > Email:   <mailto:rvaradhan at jhmi.edu> rvaradhan at jhmi.edu
> >
> > ---------------------------------------------------------------------
> > -----
> >
> >
> >
> >
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> >
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