>>>>> robin hankin <hankin.ro...@gmail.com> >>>>> on Thu, 8 Sep 2016 10:05:21 +1200 writes:
> 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. Thanks a lot, Robin, (and Oliver) ! Yes, the above is such a case where the new behavior makes much sense. And this behavior remains identical after the 71222 amendment. Martin > Best wishes > Robin > On Wed, Sep 7, 2016 at 9:49 PM, Martin Maechler <maech...@stat.math.ethz.ch> > wrote: >> >>>>> Martin Maechler <maech...@stat.math.ethz.ch> >> >>>>> 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@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel >> > -- > Robin Hankin > Neutral theorist > hankin.ro...@gmail.com > [[alternative HTML version deleted]] ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel