Use all.equal instead of identical if you want to gloss over integer/numeric class differences and minor floating point differences (and a host of others).
Bill Dunlap TIBCO Software wdunlap tibco.com On Mon, Apr 11, 2016 at 5:25 PM, Paulson, Ariel <a...@stowers.org> wrote: > Hi Jeff, > > > We are splitting hairs because R is splitting hairs, and causing us > problems. Integer and numeric are different R classes with different > properties, mathematical relationships notwithstanding. For instance, the > counterintuitive result: > > > > identical(as.integer(1), as.numeric(1)) > [1] FALSE > > > Unfortunately the reply-to chain doesn't extend far enough -- here is the > original problem: > > > > sapply(1, identical, 1) > [1] TRUE > > > sapply(1:2, identical, 1) > [1] FALSE FALSE > > > sapply(1:2, function(i) identical(as.numeric(i),1) ) > [1] TRUE FALSE > > > sapply(1:2, function(i) identical(as(i,"numeric"),1) ) > [1] FALSE FALSE > > These are the results of R's hair-splitting! > > Ariel > > ________________________________ > From: Jeff Newmiller <jdnew...@dcn.davis.ca.us> > Sent: Monday, April 11, 2016 6:49 PM > To: Bert Gunter; Paulson, Ariel > Cc: Rolf Turner; r-help@r-project.org > Subject: Re: [R] [FORGED] Re: identical() versus sapply() > > 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.4...@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 <a...@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.tur...@auckland.ac.nz] > Sent: Saturday, April 09, 2016 5:27 AM > To: Jeff Newmiller > Cc: Paulson, Ariel; 'r-help@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 > > ________________________________ > > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.