issue with nzchar() ?

string, something that I find strange. At best NA is the equivalent of
an empty string. In this sense, if you Hmisc::describe() the vector
you get, as I would expect, that in the context of character vectors
NA and '' values are considered together:

x <- c(letters, NA, '')
nchar(x)

On Mon, Aug 6, 2012 at 4:48 PM, Liviu Andronic <landronimirc at gmail.com> wrote:

string, something that I find strange. At best NA is the equivalent of
an empty string.

In this sense, if you Hmisc::describe() the vector
you get, as I would expect, that in the context of character vectors
NA and '' values are considered together:

By the way, same question holds for nchar(): Should NA values be
reported as 2-char strings, or as 0-char empty/missing values?

x <- c(letters, NA, '')
nchar(x)

 [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 0

Liviu

On Mon, Aug 6, 2012 at 4:48 PM, Liviu Andronic <landronimirc at gmail.com> wrote:

string, something that I find strange. At best NA is the equivalent of
an empty string. In this sense, if you Hmisc::describe() the vector
you get, as I would expect, that in the context of character vectors
NA and '' values are considered together:

By the way, same question holds for nchar(): Should NA values be
reported as 2-char strings, or as 0-char empty/missing values?

x <- c(letters, NA, '')
nchar(x)

 [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 0


Liviu

ifelse(is.na(x), NA, nzchar(x))

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
project.org] On Behalf Of Bert Gunter
Sent: Monday, August 06, 2012 10:43 AM
To: Liviu Andronic
Cc: r-help at r-project.org Help
Subject: Re: [R] issue with nzchar() ?

Liviu:

Well, as usual, to a certain extent this is arbitrary and the only
issue is whether it is documented correctly.

To me, NA (of whatever mode) means ""indeterminate" or "unknown," so
since "" is known and of length 0, I would have expected NA as a
return. But the point is, not what our particular tastes are ("You say
'tomayto', I say 'tomahto,' an old song goes), but what the docs say.
And in both cases, they tell you exactly what you'll get.

For nchar(): " an integer vector giving the sizes of each element,
currently always 2 for missing values (for NA)"

and for nzchar: "a logical vector of the same length as x, true if and
only if the element has non-zero length." (note the 'only if').

So I see no error or inconsistencies anywhere.

-- Bert

On Mon, Aug 6, 2012 at 7:53 AM, Liviu Andronic <landronimirc at gmail.com>
wrote:

On Mon, Aug 6, 2012 at 4:48 PM, Liviu Andronic

<landronimirc at gmail.com> wrote:

string, something that I find strange. At best NA is the equivalent

of

an empty string. In this sense, if you Hmisc::describe() the vector
you get, as I would expect, that in the context of character vectors
NA and '' values are considered together:

By the way, same question holds for nchar(): Should NA values be
reported as 2-char strings, or as 0-char empty/missing values?

x <- c(letters, NA, '')
nchar(x)

 [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 0


Liviu

guide.html

--

Bert Gunter
Genentech Nonclinical Biostatistics

Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-
biostatistics/pdb-ncb-home.htm

On Mon, Aug 6, 2012 at 9:53 AM, Liviu Andronic <landronimirc at gmail.com> wrote:

On Mon, Aug 6, 2012 at 4:48 PM, Liviu Andronic <landronimirc at gmail.com> wrote:

string, something that I find strange. At best NA is the equivalent of
an empty string.

Certainly not to my mind, unless you think that zero and NA should be
the same for integers and doubles as well. NA (in whatever form) is,
to my mind, _unknown_ which is very different than knowing 0.

I'm not sure why that's the case, but it's documented on the help page
(under value):

 For ?nchar?, an integer vector giving the sizes of each element,
     currently always ?2? for missing values (for ?NA?).

My guess is that it's this way for back-compatability from a time when
there probably wasn't a proper NA_character_ (that's the parser
literal for a character NA) and they really were just "NA" (the
string) -- perhaps in some far distant R 3.0 we'll see
nchar(NA_character_) = NA_integer_