ripley@stats.ox.ac.uk wrote:
On Tue, 14 May 2002, Dirk Eddelbuettel wrote:
With a (late prerelease of) 1.5.0 on Windows, using sprintf on NaN yields garbage when the number of decimal is specified while it works fine for NA:
sprintf("%.2f", NA)
[1] "0.00"
I get that on Linux too, but why is it fine? See below.
sprintf("%.2f", NaN)
[1] "-1.#J" Not specifying the decimal precision lets both print garbage:
sprintf("%f", NaN)
[1] "-1.#IND00"
sprintf("%f", NA)
[1] "-1.#QNAN0" Is this a bug or a feature?
Remember that NA is logical, so this is not correct usage. Not that the correct usage works very much better .... The C code says /* Simple wrapper for C sprintf function: does very little checking to see that the format conversion character and the argument are compatible. This is the user's responsibility! */ and I think that should be on the help page. If it were, this is a feature.
Naturally it's a feature! But I agree that an extra sentance or two on
the help page would be a good idea. I suggest appending the following
as a new paragraph to the Value section:
As \code{sprintf} is simply a wrapper for the C function of the same
name, it is the user's responsibility to ensure that the objects passed
in \code{\dots} correspond to the format. Otherwise the resulting
string may contain garbage. For example, the typical R numeric object
is a float not an integer (see Examples, below). Likewise, C does not
recognise special values like \code{NA}, so \code{sprintf("Our survey
said: %f", NA)} is not going to work as you might want.
I've cc'ed this to r-bugs. Jonathan.
Jonathan Rougier Science Laboratories Department of Mathematical Sciences South Road University of Durham Durham DH1 3LE tel: +44 (0)191 374 2361, fax: +44 (0)191 374 7388 http://www.maths.dur.ac.uk/stats/people/jcr/jcr.html -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-devel-request@stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._