Inconsistency in handling of numeric input with %d by sprintf

Yes, what Joris posts about is exactly what I noted in my March 9th post to
R-devel. The behaviour is sort of documented, but not in the clearest
manner (in my opinion). Like I say, my ultimate conclusion was that the
silent coercion of numerics to integers by sprintf() was a handy
convenience, but not one that should be relied about to always work
predictably.

On Tue, May 23, 2017 at 10:02 AM, Michael Chirico <michaelchirico4 at gmail.com

wrote:
https://github.com/Rdatatable/data.table/issues/2171

The fix was easy, it's just surprising to see the behavior change almost
on a whim. Just wanted to point it out in case this is unknown behavior,
but Evan seems to have found this as well.

On Tue, May 23, 2017 at 12:00 PM, Michael Chirico <
michaelchirico4 at gmail.com> wrote:

Astute observation. And of course we should be passing integer when we
use %d. It's an edge case in how we printed ITime objects in data.table:


On Tue, May 23, 2017 at 11:53 AM, Joris Meys <jorismeys at gmail.com> wrote:

I initially thought this is "documented behaviour". ?sprintf says:

Numeric variables with __exactly integer__ values will be coerced to
integer. (emphasis mine).

Turns out this only works when the first value is numeric and not NA, as
shown by the following example:

sprintf("%d", as.numeric(c(NA,1)))

Error in sprintf("%d", as.numeric(c(NA, 1))) :
   invalid format '%d'; use format %f, %e, %g or %a for numeric objects

sprintf("%d", as.numeric(c(1,NA)))

[1] "1"  "NA"

So the safest thing is indeed passing the right type, but the behaviour
is indeed confusing. I checked this on both Windows and Debian, and on both
systems I get the exact same response.

Cheers
Joris

On Tue, May 23, 2017 at 4:53 PM, Evan Cortens <ecortens at mtroyal.ca>
wrote:

Hi Michael,

I posted something on this topic to R-devel several weeks ago, but never
got a response. My ultimate conclusion is that sprintf() isn't super
consistent in how it handles coercion: sometimes it'll coerce real to
integer without complaint, other times it won't. (My particular email
had
to do with the vectors longer than 1 and their positioning vis-a-vis the
format string.) The safest thing is just to pass the right type. In this
case, sprintf('%d', as.integer(NA_real_)) works.

Best,

Evan

On Fri, May 19, 2017 at 9:23 AM, Michael Chirico <
michaelchirico4 at gmail.com>
wrote:

Consider

#as.numeric for emphasis
sprintf('%d', as.numeric(1))
# [1] "1"

vs.

sprintf('%d', NA_real_)

  Error in sprintf("%d", NA_real_) :

    invalid format '%d'; use format %f, %e, %g or %a for numeric object
I understand the error is correct, but if it works for other numeric

input,

why doesn't R just coerce NA_real_ to NA_integer_?

Michael Chirico

         [[alternative HTML version deleted]]

--
Evan Cortens, PhD
Institutional Analyst - Office of Institutional Analysis
Mount Royal University
403-440-6529

         [[alternative HTML version deleted]]

--
Joris Meys
Statistical consultant

Ghent University
Faculty of Bioscience Engineering
Department of Mathematical Modelling, Statistics and Bio-Informatics

tel :  +32 (0)9 264 61 79 <+32%209%20264%2061%2079>
Joris.Meys at Ugent.be
-------------------------------
Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php

	[[alternative HTML version deleted]]