how to include 'NA's in xtabs?

test <- c(1,2,3,1,2,3,NA,NA,1,2,3)
test

table(test)

table(test, exclude=NULL)

test <- factor(test)
table(test)

table(test, exclude=NULL)

That's ok if i do something like xtabs(~f1). Thanks.
What about xtabs(w~f1+f2)? If i need to do crosstabulation
and factor variables contains NA's?

I want to repeat my second question: how to use 'na.action'
argument in xtabs? Can anybody explain, how is it works?


Petr Pikal wrote:

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!

Cheers
Petr Pikal
petr.pikal at precheza.cz
p.pik at volny.cz




.