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

[Prof Brian Ripley]

This is not a bug, and it is described in the section on USER-VISIBLE
CHANGES in the NEWS file!

Hint: consider the setting of the quote argument when printing.


On Tue, 30 Apr 2002, David Kane  <David Kane wrote:

> 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

But then you would have though NA meant Nabisco.

>
> 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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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595


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