[R] display of character NA's in a dataframe in 1.5.0

[David Kane <David Kane]

I understand that NA's in character vectors are displayed differently than NA's
in factor vectors.

> c("x", NA, "y")
[1] "x" NA  "y"
> as.factor(c("x", NA, "y"))
[1] x    <NA> y   
Levels:  x y 

That seems sensible enough. But shouldn't I see the same behavior in a dataframe?

> test <- data.frame(a = c("x", NA, "y"))
> test
     a
1    x
2   <NA>
3    y
> is.factor(test$a)
[1] TRUE
> is.character(test$a)
[1] FALSE

This behavior is correct since R coerces `a' to be a factor as it constructs
the test dataframe. But consider what happens when I force `a' to be character:

> test$a <- as.character(test$a)
> is.factor(test$a)
[1] FALSE
> is.character(test$a)
[1] TRUE
> test
     a
1    x
2   <NA>
3    y

The display is the same. I would have expected it to be something like:

> test
     a
1    x
2   NA
3    y

If this is a bug, please let me know and I would be happy to submit it as
such. But, I suspect that it is more likely that there is something that I
don't fully understand about NA's and dataframes.


> R.version
         _                   
platform sparc-sun-solaris2.6
arch     sparc               
os       solaris2.6          
system   sparc, solaris2.6   
status                       
major    1                   
minor    5.0                 
year     2002                
month    04                  
day      29                  
language R                   

Thanks,

Dave Kane
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