'summary' with logicals (PR#2629)

Consider

oj <- data.frame(x = c(TRUE, FALSE, NA))
oj

x
1  TRUE
2 FALSE
3    NA

summary(oj)

x          
 Mode :logical  
 FALSE:1        
 TRUE :1        

But

oj$x <- factor(oj$x)
summary(oj)

x    
 FALSE:1  
 TRUE :1  
 NA's :1  

My point is that NA's should be reported for logicals like they are for 
other data types.

Göran
---
 Göran Broström                    tel: +46 90 786 5223
 Department of Statistics          fax: +46 90 786 6614
 Umeå University                   http://www.stat.umu.se/egna/gb/
 SE-90187 Umeå, Sweden             e-mail: gb@stat.umu.se