[R] [FORGED] Re: identical() versus sapply()

[Jeff Newmiller]

Hypothesis regarding the thought process: integer is a perfect subset of numeric, so why split hairs? 
-- 
Sent from my phone. Please excuse my brevity.

On April 11, 2016 12:36:56 PM PDT, Bert Gunter <bgunter.4567 at gmail.com> wrote:
>Indeed!
>
>Slightly simplified to emphasize your point:
>
>> class(as(1:2,"numeric"))
>[1] "integer"
>
>> class(as.numeric(1:2))
>[1] "numeric"
>
>whereas in ?as it says:
>
>"Methods are pre-defined for coercing any object to one of the basic
>datatypes. For example, as(x, "numeric") uses the existing as.numeric
>function. "
>
>I suspect this is related to my ignorance of S4 classes (i.e. as() )
>and how they relate to S3 classes, but I certainly don't get it
>either.
>
>Cheers,
>Bert
>
>
>
>Bert Gunter
>
>"The trouble with having an open mind is that people keep coming along
>and sticking things into it."
>-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>
>
>On Mon, Apr 11, 2016 at 9:30 AM, Paulson, Ariel <apa at stowers.org>
>wrote:
>> Ok, I see the difference between 1 and 1:2, I'll just leave it as one
>of those "only in R" things.
>>
>> But it seems then, that as.numeric() should guarantee a FALSE
>outcome, yet it does not.
>>
>> To build on what Rolf pointed out, I would really love for someone to
>explain this one:
>>
>>> str(1)
>>  num 1
>>
>>> str(1:2)
>>  int [1:2] 1 2
>>
>>> str(as.numeric(1:2))
>>  num [1:2] 1 2
>>
>>> str(as(1:2,"numeric"))
>>  int [1:2] 1 2
>>
>> Which doubly makes no sense.  1) Either the class is "numeric" or it
>isn't; I did not call as.integer() here.  2) method of recasting should
>not affect final class.
>>
>> Thanks,
>> Ariel
>>
>>
>> -----Original Message-----
>> From: Rolf Turner [mailto:r.turner at auckland.ac.nz]
>> Sent: Saturday, April 09, 2016 5:27 AM
>> To: Jeff Newmiller
>> Cc: Paulson, Ariel; 'r-help at r-project.org'
>> Subject: Re: [FORGED] Re: [R] identical() versus sapply()
>>
>> On 09/04/16 16:24, Jeff Newmiller wrote:
>>> I highly recommend making friends with the str function. Try
>>>
>>> str( 1 )
>>> str( 1:2 )
>>
>> Interesting.  But to me counter-intuitive.  Since R makes no
>distinction between scalars and vectors of length 1 (or more accurately
>I think, since in R there is *no such thing as a scalar*, only a vector
>of length
>> 1) I don't see why "1" should be treated in a manner that is
>categorically different from the way in which "1:2" is treated.
>>
>> Can you, or someone else with deep insight into R and its rationale,
>explain the basis for this difference in treatment?
>>
>>> for the clue you need, and then
>>>
>>> sapply( 1:2, identical, 1L )
>>
>> cheers,
>>
>> Rolf
>>
>> --
>> Technical Editor ANZJS
>> Department of Statistics
>> University of Auckland
>> Phone: +64-9-373-7599 ext. 88276
>>
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