[Rd] multiple issues with is.unsorted()

[William Dunlap]

>    >>> is.unsorted(NA)
>    >> [1] NA
>    >> => Contradicts "all objects of length 0 or 1 are sorted".
>
> Ok.  I really think we should change the above.
> If NA is for a missing number, it still cannot be unsorted if it
> is of length one.
> 
> --> the above will give FALSE  "real soon now".

It depends what you are using the result of is.unsorted() for.  If you want
to know if you can save time by not calling x<-sort(x)  then is.unsorted(NA)
should not say that NA is sorted, as sort(NA) has length 0.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: r-devel-bounces at r-project.org [mailto:r-devel-bounces at r-project.org] On Behalf
> Of Martin Maechler
> Sent: Wednesday, April 24, 2013 8:41 AM
> To: Hervé Pagès; R-devel at stat.math.ethz.ch
> Cc: Martin Maechler
> Subject: Re: [Rd] multiple issues with is.unsorted()
> 
> More comments .. see inline
> 
> >>>>> Martin Maechler <maechler at stat.math.ethz.ch>
> >>>>>     on Wed, 24 Apr 2013 11:29:39 +0200 writes:
> 
>     > Dear Herve,
> >>>>> Hervé Pagès <hpages at fhcrc.org>
> >>>>> on Tue, 23 Apr 2013 23:09:21 -0700 writes:
> 
>     >> Hi, In the man page for is.unsorted():
> 
>     >> Value:
> 
>     >> A length-one logical value.  All objects of length 0 or 1
>     >> are sorted: the result will be ‘NA’ for objects of length
>     >> 2 or more except for atomic vectors and objects with a
>     >> class (where the ‘>=’ or ‘>’ method is used to compare
>     >> ‘x[i]’ with ‘x[i-1]’ for ‘i’ in ‘2:length(x)’).
> 
>     >> This contains many incorrect statements:
> 
>     >>> length(NA)
>     >> [1] 1
>     >>> is.unsorted(NA)
>     >> [1] NA
>     >>> length(list(NA))
>     >> [1] 1
>     >>> is.unsorted(list(NA))
>     >> [1] NA
> 
>     >> => Contradicts "all objects of length 0 or 1 are sorted".
> 
> Ok.  I really think we should change the above.
> If NA is for a missing number, it still cannot be unsorted if it
> is of length one.
> 
> --> the above will give FALSE  "real soon now".
> 
>     >>> is.unsorted(raw(2))
>     >> Error in is.unsorted(raw(2)) : unimplemented type 'raw'
>     >> in 'isUnsorted'
> 
>     >> => Doesn't agree with the doc (unless "except for atomic
>     >> vectors" means "it might fail for atomic vectors").
> 
> Well, the doc says about 'x'
> |  \item{x}{an \R object with a class or a numeric, complex, character or
> |    logical vector.}
> so strictly, is.unsorted() is not to be used on raw vectors.
> 
> However I think you have a point:
> Raw vectors didn't exist when  is.unsorted()  was
> invented, so where not considered back then.
> Originally,  raw vectors were really almost only there for
> storage, i.e. basically read and write, but now we have
> as '<' , '<=' '=='  etc  working well for raw() ,
> we could allow  is.unsorted() to work, too.
> 
> Note however, that if you try to sort(<raw>) you also always get
> an error about sort() not being implemented for raw(),...
> something we could arguably reconsider, as we admitted the
> relational operators (< <= == >= >  != ) to work.
> {{anyone donating patches to R-devel for sort()ing raw ?}}
> 
> 
>     >>> setClass("A", representation(aa="integer"))
>     >>> new("A", aa=4:1)
>     >>> length(a)
>     >> [1] 1
> 
>     >>> is.unsorted(a)
>     >> [1] FALSE
>     >>  Warning message: In is.na(x) : is.na() applied
>     >> to non-(list or vector) of type 'S4'
> 
>     >> => Ok, but it's arguable the warning is useful/justified
>     >> from a user point of view. The warning *seems* to suggest
>     >> that defining an "is.na" method for my objects is
>     >> required for is.unsorted() to work properly but the doc
>     >> doesn't make this clear.
> 
> you are right.
> We are going to improve on this, at least the documentation.
> 
> 
> [.................]
> 
> The S4 part I've already started addressing in the last reply.
> (and we may get back to that.. )
> 
> [.................]
> 
> Martin
> 
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