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

[Kosenkov Kirill]

Thanks for your reply, but i dont want to transform my data
with 'factor' or anything else. I really need 'NA's as NA's
and i dont need them as levels of factor.

I just seeking possibility to compute count of 'NA's with
'xtabs' without transforming my data. Maybe 'na.action' argument
in 'xtabs' may help? But i dont know how to use it.

Any suggestions?

Sundar Dorai-Raj wrote:

> 
> 
> 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
> 
> 
> 
> .
>