[R] how to force a table to be square?

[peter dalgaard]

On Jul 22, 2010, at 4:00 PM, Liat wrote:

> 
> Hi guys,
> I hope you can help me with this.
> Here is the problem:
> I have some data (myData) that looks similar to this:
> 
>     [,1] [,2] [,3] [,4]
> [1,] "A"  "A"  "B"  "B" 
> [2,] "B"  "B"  "B"  "B" 
> [3,] "C"  "C"  "C"  "C" 
> 
> When I build a contingency table for the first and second row using:
> tb <- table(myData[1,  ], myData[2,  ], useNA="ifany")
> I get:
>  B
>  A 2
>  B 2
> But - I would like to also see "C" there (with a zero).
> Actually, I would like to give a list of n characters that would be used to
> build an n*n table and the data for this table should then come from myData
> (and if there are characters in my list that do not appear in the data at
> all I would like to see a zero row or a zero column).
> Is that possible to do?
> What would be the simplest way?
> Many many thanks!!!
> Liat.

Just convert each character vector to a factor with the appropriate level set, as in

table(factor(myData[1,  ], levels=c("A","B","C")))

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-- 
Peter Dalgaard
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