R help - May 2003 - how to include 'NA's in xtabs?

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

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!

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 ...
> 
The key is here. Should be 3 levels if you want NAs included.
> 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$P67
>    -    +   NA
>  779 1318  137
> 
> I am trying xtabs(~x$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!
> 

Try this:

x$P67 = factor(x$P67, exclude = NULL)
xtabs(~x$P67)


Here's an example:
R> x = factor(c(1:2, NA), exclude = NULL, labels = c("+",
"-", "0"))
R> xtabs(~ x)
x
+ - 0
1 1 1

Sundar

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!
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
Cheers
Petr Pikal
petr.pikal at precheza.cz
p.pik at volny.cz