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

[Paulson, Ariel]

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

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