[R] how to include 'NA's in xtabs?

[Petr Pikal]

Hi

On 15 May 2003 at 0:18, Kosenkov Kirill wrote:

> Hello!
> 
> I have a dataset with NA's in some variables (factors), for example: $
> P67 : Factor w/ 2 levels "-","+": NA 2 1 NA NA 2 1 1 2 NA ...
> 
> I need to use 'xtabs' like
> xtabs(~x$P67)
> It works well and produces something like this:
> x$P67
>     -    +
>   779 1318
> but i want to compute NA's too, like this:
> x$P67
>     -    +   NA
>   779 1318  137

what about using summary instead of xtabs

> summary(ostbet$delka)
 159  160 NA's 
   5   22    3 

> xtabs(~ostbet$delka)
ostbet$delka
159 160 
  5  22 




> 
> I am trying xtabs(~x$P67, exclude=NULL) but xtabs does not compute
> 'NA's in this case too.
> 
> I do not want to transform my data (do not want to do any 
> substitution on NA's).
> 
> How i can say 'xtabs' to compute NA-values?
> 
> and second question: how to use argument 'na.action' in 'xtabs'?
> 'xtabs' help page does not explain this.
> 
> Thanks!
> 
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Cheers
Petr Pikal
petr.pikal at precheza.cz
p.pik at volny.cz