[Rd] R (development) changes in arith, logic, relop with (0-extent) arrays
Oliver Keyes
ironholds at gmail.com
Thu Sep 8 03:59:00 CEST 2016
+1. Very grateful; more consistency is always great :)
On Wednesday, 7 September 2016, robin hankin <hankin.robin at gmail.com> wrote:
> Martin
>
> I'd like to make a comment; I think that R's behaviour on 'edge' cases like
> this is an important thing and it's great that you are working on it.
>
> I make heavy use of zero-extent arrays, chiefly because the dimnames are an
> efficient and logical way to keep track of certain types of information.
>
> If I have, for example,
>
> a <- array(0,c(2,0,2))
> dimnames(a) <- list(name=c('Mike','Kevin'),NULL,item=c("hat","scarf"))
>
>
> Then in R-3.3.1, 70800 I get
>
> > a>0
> logical(0)
> >
>
> But in 71219 I get
>
> > a>0
> , , item = hat
>
>
> name
> Mike
> Kevin
>
> , , item = scarf
>
>
> name
> Mike
> Kevin
>
> (which is an empty logical array that holds the names of the people and
> their clothes). I find the behaviour of 71219 very much preferable because
> there is no reason to discard the information in the dimnames.
>
>
> Best wishes
>
> Robin
>
>
>
>
> On Wed, Sep 7, 2016 at 9:49 PM, Martin Maechler <
> maechler at stat.math.ethz.ch <javascript:;>>
> wrote:
>
> > >>>>> Martin Maechler <maechler at stat.math.ethz.ch <javascript:;>>
> > >>>>> on Tue, 6 Sep 2016 22:26:31 +0200 writes:
> >
> > > Yesterday, changes to R's development version were committed,
> > relating
> > > to arithmetic, logic ('&' and '|') and
> > > comparison/relational ('<', '==') binary operators
> > > which in NEWS are described as
> >
> > > SIGNIFICANT USER-VISIBLE CHANGES:
> >
> > > [.............]
> >
> > > • Arithmetic, logic (‘&’, ‘|’) and comparison (aka
> > > ‘relational’, e.g., ‘<’, ‘==’) operations with arrays now
> > > behave consistently, notably for arrays of length zero.
> >
> > > Arithmetic between length-1 arrays and longer non-arrays had
> > > silently dropped the array attributes and recycled. This
> > > now gives a warning and will signal an error in the future,
> > > as it has always for logic and comparison operations in
> > > these cases (e.g., compare ‘matrix(1,1) + 2:3’ and
> > > ‘matrix(1,1) < 2:3’).
> >
> > > As the above "visually suggests" one could think of the changes
> > > falling mainly two groups,
> > > 1) <0-extent array> (op) <non-array>
> > > 2) <1-extent array> (arith) <non-array of length != 1>
> >
> > > These changes are partly non-back compatible and may break
> > > existing code. We believe that the internal consistency gained
> > > from the changes is worth the few places with problems.
> >
> > > We expect some package maintainers (10-20, or even more?) need
> > > to adapt their code.
> >
> > > Case '2)' above mainly results in a new warning, e.g.,
> >
> > >> matrix(1,1) + 1:2
> > > [1] 2 3
> > > Warning message:
> > > In matrix(1, 1) + 1:2 :
> > > dropping dim() of array of length one. Will become ERROR
> > >>
> >
> > > whereas '1)' gives errors in cases the result silently was a
> > > vector of length zero, or also keeps array (dim & dimnames) in
> > > cases these were silently dropped.
> >
> > > The following is a "heavily" commented R script showing (all ?)
> > > the important cases with changes :
> >
> > > ------------------------------------------------------------
> > ----------------
> >
> > > (m <- cbind(a=1[0], b=2[0]))
> > > Lm <- m; storage.mode(Lm) <- "logical"
> > > Im <- m; storage.mode(Im) <- "integer"
> >
> > > ## 1. -------------------------
> > > try( m & NULL ) # in R <= 3.3.x :
> > > ## Error in m & NULL :
> > > ## operations are possible only for numeric, logical or complex
> > types
> > > ##
> > > ## gives 'Lm' in R >= 3.4.0
> >
> > > ## 2. -------------------------
> > > m + 2:3 ## gave numeric(0), now remains matrix identical to m
> > > Im + 2:3 ## gave integer(0), now remains matrix identical to Im
> > (integer)
> >
> > > m > 1 ## gave logical(0), now remains matrix identical to Lm
> > (logical)
> > > m > 0.1[0] ## ditto
> > > m > NULL ## ditto
> >
> > > ## 3. -------------------------
> > > mm <- m[,c(1:2,2:1,2)]
> > > try( m == mm ) ## now gives error "non-conformable arrays",
> > > ## but gave logical(0) in R <= 3.3.x
> >
> > > ## 4. -------------------------
> > > str( Im + NULL) ## gave "num", now gives "int"
> >
> > > ## 5. -------------------------
> > > ## special case for arithmetic w/ length-1 array
> > > (m1 <- matrix(1,1,1, dimnames=list("Ro","col")))
> > > (m2 <- matrix(1,2,1, dimnames=list(c("A","B"),"col")))
> >
> > > m1 + 1:2 # -> 2:3 but now with warning to "become ERROR"
> > > tools::assertError(m1 & 1:2)# ERR: dims [product 1] do not match
> the
> > length of object [2]
> > > tools::assertError(m1 < 1:2)# ERR: (ditto)
> > > ##
> > > ## non-0-length arrays combined with {NULL or double() or ...}
> *fail*
> >
> > > ### Length-1 arrays: Arithmetic with |vectors| > 1 treated array
> > as scalar
> > > m1 + NULL # gave numeric(0) in R <= 3.3.x --- still, *but* w/
> > warning to "be ERROR"
> > > try(m1 > NULL) # gave logical(0) in R <= 3.3.x --- an *error*
> > now in R >= 3.4.0
> > > tools::assertError(m1 & NULL) # gave and gives error
> > > tools::assertError(m1 | double())# ditto
> > > ## m2 was slightly different:
> > > tools::assertError(m2 + NULL)
> > > tools::assertError(m2 & NULL)
> > > try(m2 == NULL) ## was logical(0) in R <= 3.3.x; now error as
> above!
> >
> > > ------------------------------------------------------------
> > ----------------
> >
> >
> > > Note that in R's own 'nls' sources, there was one case of
> > > situation '2)' above, i.e. a 1x1-matrix was used as a "scalar".
> >
> > > In such cases, you should explicitly coerce it to a vector,
> > > either ("self-explainingly") by as.vector(.), or as I did in
> > > the nls case by c(.) : The latter is much less
> > > self-explaining, but nicer to read in mathematical formulae, and
> > > currently also more efficient because it is a .Primitive.
> >
> > > Please use R-devel with your code, and let us know if you see
> > > effects that seem adverse.
> >
> > I've been slightly surprised (or even "frustrated") by the empty
> > reaction on our R-devel list to this post.
> >
> > I would have expected some critique, may be even some praise,
> > ... in any case some sign people are "thinking along" (as we say
> > in German).
> >
> > In the mean time, I've actually thought along the one case which
> > is last above: The <op> (binary operation) between a
> > non-0-length array and a 0-length vector (and NULL which should
> > be treated like a 0-length vector):
> >
> > R <= 3.3.1 *is* quite inconsistent with these:
> >
> >
> > and my proposal above (implemented in R-devel, since Sep.5) would give an
> > error for all these, but instead, R really could be more lenient here:
> > A 0-length result is ok, and it should *not* inherit the array
> > (dim, dimnames), since the array is not of length 0. So instead
> > of the above [for the very last part only!!], we would aim for
> > the following. These *all* give an error in current R-devel,
> > with the exception of 'm1 + NULL' which "only" gives a "bad
> > warning" :
> >
> > ------------------------
> >
> > m1 <- matrix(1,1)
> > m2 <- matrix(1,2)
> >
> > m1 + NULL # numeric(0) in R <= 3.3.x ---> OK ?!
> > m1 > NULL # logical(0) in R <= 3.3.x ---> OK ?!
> > try(m1 & NULL) # ERROR in R <= 3.3.x ---> change to logical(0) ?!
> > try(m1 | double())# ERROR in R <= 3.3.x ---> change to logical(0) ?!
> > ## m2 slightly different:
> > try(m2 + NULL) # ERROR in R <= 3.3.x ---> change to double(0) ?!
> > try(m2 & NULL) # ERROR in R <= 3.3.x ---> change to logical(0) ?!
> > m2 == NULL # logical(0) in R <= 3.3.x ---> OK ?!
> >
> > ------------------------
> >
> > This would be slightly more back-compatible than the currently
> > implemented proposal. Everything else I said remains true, and
> > I'm pretty sure most changes needed in packages would remain to be done.
> >
> > Opinions ?
> >
> >
> >
> > > In some case where R-devel now gives an error but did not
> > > previously, we could contemplate giving another "warning
> > > .... 'to become ERROR'" if there was too much breakage, though
> > > I don't expect that.
> >
> >
> > > For the R Core Team,
> >
> > > Martin Maechler,
> > > ETH Zurich
> >
> > ______________________________________________
> > R-devel at r-project.org <javascript:;> mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-devel
> >
>
>
>
> --
> Robin Hankin
> Neutral theorist
> hankin.robin at gmail.com <javascript:;>
>
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>
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