[R-SIG-Mac] Unexpected behavior from sprintf()

[David Winsemius]

On Apr 24, 2012, at 6:07 PM, Duncan Murdoch wrote:

> On 12-04-24 4:24 PM, Joran Elias wrote:
>> I stumbled across this by accident from this StackOverflow question:
>>
>> http://stackoverflow.com/q/10300325/324364
>>
>> and a subsequent discussion in the StackOverflow R chat room:
>>
>> http://chat.stackoverflow.com/transcript/message/3431991#3431991
>>
>> The issue is the output from the following code:
>>
>> sprintf('%05s',as.character(1:5))
>>
>> It appears that when this is run in OS X in either 2.14.2 or  
>> 2.15.0, the
>> output is:
>>
>> [1] "00001" "00002" "00003" "00004" "00005"
>>
>> whereas when it is run on other platforms (I saw examples from  
>> various
>> Windows versions and one user on Ubuntu, all using 2.15.0 I  
>> believe) you
>> get:
>>
>> [1] "    1" "    2" "    3" "    4" "    5"
>>
>> There was some uncertainty as to which behavior is "expected". Does  
>> anyone
>> have any insight into which behavior is "correct" and whether this  
>> is a bug
>> or not?
>
> I would say it's probably user-error:  the docs don't say what that  
> should do.   Numeric formats would pad with zeros, but I don't think  
> it says what would happen if you ask for zero padding on a string.

The ?sprintf help page indicated that non-character R objects will get  
passed though `as.character` on their way to the system facility. In  
the case of a factor variable which has levels with numeric-coercible  
values, we Mac users get very sensible output. Likewise we get very  
sensible output from character vectors, and when a format of "05i" is  
used the fact that we get the numeric encoding for factors is likewise  
no surprise.

-- 

David.
>
> In any case, R just passes a format like that to the C printf  
> function.  So if it's a bug, it's in the C run-time, not in R.


>
> Duncan
>
>>
>> - Joran
>>
>> 	[[alternative HTML version deleted]]
>>
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David Winsemius, MD
West Hartford, CT