R help - Aug 2011 - Showing zero frequencies with xtabs

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On Aug 30, 2011, at 10:04 , Luca Meyer wrote:
> Hi,
> 
> Does anyone know how to show zero frequencies variable levels with the
xtabs command? They show with the table(x,y) command but I need to apply weight
to frequency tables and I also need to cbind several tables together, which
implies that they all need to show the same number of rows.
Are you sure you are doing the same thing as with table(). I'd expect it to
work if you ensure that the variables are factors:
> library(ISwR)
> xtabs(~sex+menarche,data=juul)
   menarche
sex   1   2
  2 369 335
> juul$sex <- factor(juul$sex,levels=1:2)
> xtabs(~sex+menarche,data=juul)
   menarche
sex   1   2
  1   0   0
  2 369 335


> 
> Alternatively, do you know how to column bind tables with different number
of rows? I cannot use merge as it requires daata.frame and that modifies the
look of the banner table I am trying to create...
> 
> Thanks,
> Luca
> 
> 
> Mr. Luca Meyer
> www.lucameyer.com
> R version 2.13.1 (2011-07-08)
> Mac OS X 10.6.8
> 
> 
> 
> 
> 
> 
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> 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.
-- 
Peter Dalgaard, Professor
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com

Hi
> 
> Hi,
> 
> Does anyone know how to show zero frequencies variable levels with the 
> xtabs command? They show with the table(x,y) command but I need to apply 
> weight to frequency tables and I also need to cbind several tables 
> together, which implies that they all need to show the same number of 
rows. 

Do you use factors?

x<-sample(letters[1:5], 20, replace=T)
xtabs(~x)
x
a b c d e 
2 1 5 4 8 

x.f<-factor(x)
x[x=="b"]<-NA
x.f[x.f=="b"]<-NA
> xtabs(~x)
x
a c d e 
2 5 4 8 
> xtabs(~x.f)
x.f
a b c d e 
2 0 5 4 8 

With factors you can specify also non existent levels so they shall appear 
as zeroes in table or xtabs.

Regards
Petr
> 
> Alternatively, do you know how to column bind tables with different 
number
> of rows? I cannot use merge as it requires daata.frame and that modifies 
> the look of the banner table I am trying to create...
> 
> Thanks,
> Luca
> 
> 
> Mr. Luca Meyer
> www.lucameyer.com
> R version 2.13.1 (2011-07-08)
> Mac OS X 10.6.8
> 
> 
> 
> 
> 
> 
> 
>    [[alternative HTML version deleted]]
> 
> ______________________________________________
> 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.