It gives me a headache, too! I think you'll have to wait for a more
expert user than me to supply explanations of these behaviors and
their rationales.
-s
On 6/26/09, Craig P. Pyrame <crap...@gmail.com> wrote:
> Stavros Macrakis wrote:
>> On Thu, Jun 25, 2009 at 12:47 PM, Craig P. Pyrame<crap...@gmail.com>
>> wrote:
>>
>>> The man page Stavros quotes states that the class attribute of the result
>>> is
>>> taken from 'test', which clearly is not the case:
>>>
>>
>> Actually, the behavior is documented pretty clearly:
>>
>> The mode of the answer will be coerced from logical to
>> accommodate first any values taken from 'yes' and then
>> any values taken from 'no'.
>>
>> Whether this is a good design or not is another issue.... Perhaps the
>> justification is that it avoids evaluating the yes or no arguments (to
>> determine their class) in cases where their value is not needed.
>>
>
> Thank you for pointing me to this. Now I get a headache from trying to
> figure out what does mode have to do with class - I thought that the
> class of the result should be that of test, and that the mode is
> something entirely different. Why does coercing the mode also affect
> the class? If the man page said "The class attribute is taken from
> test, and it will be coerced ..." or "The mode of the result is taken
> from test, and it will be coreced ...", would this be wrong? What is
> the class-mode mixture about?
>
> Why does this fail:
>
> > r = as.raw(TRUE)
> > ifelse(TRUE, r, r) => error
>
> This gives an error which I take for saying that raw cannot be coerced
> to logical, but yes it can:
>
> > as.logical(r) => TRUE
>
> and raw can even be used as the condition vector in ifelse:
>
> > ifelse(r, 1, 2) => 1
>
> Best regards,
> Craig
>
>
>> Example:
>>
>> ifelse(c(T,F),1,"a") => c("1","a")
>>
>> This has the same effect as
>>
>> res <- c(T,F)
>> res[1] <- 1
>> res[2] <- "a"
>>
>> which is in fact pretty much the way it is implemented.
>>
>>
>>> And also, I find myself incapable of making sense of the "may" in "the
>>> mode
>>> of the result may depend on the value of 'test'" - may in what sense?
>>>
>>
>> See the examples at the end of ? ifelse
>>
>> -s
>>
>
>
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
