Re: [Rd] head.matrix can return 1000s of columns -- limit to n or add new argument?
Hi Martin,
On Wed, Oct 30, 2019 at 4:30 AM Martin Maechler
wrote:
> > Gabriel Becker
> > on Tue, 29 Oct 2019 12:43:15 -0700 writes:
>
> > Hi all,
> > So I've started working on this and I ran into something that I
> didn't
> > know, namely that for x a multi-dimensional (2+) array, head(x) and
> tail(x)
> > ignore dimension completely, treat x as an atomic vector, and return
> an
> > (unclassed) atomic vector:
>
> Well, that's (3+), not "2+" .
>
You're correct, of course. Apologies for that.
>
> But I did write (on Sep 17 in this thread!)
>
> > The current source for head() and tail() and all their methods
> > in utils is just 83 lines of code {file utils/R/head.R minus
> > the initial mostly copyright comments}.
>
> and if've ever looked at these few dozen of R code lines, you'll
> have seen that we just added two simple utilities with a few
> reasonable simple methods. To treat non-matrix (i.e. non-2d)
> arrays as vectors, is typically not unreasonable in R, but
> indeed with your proposals (in this thread), such non-2d arrays
> should be treated differently either via new head.array() /
> tail.array() methods ((or -- only if it can be done more nicely -- by
> the default method)).
>
I hope you didn't construe my describing surprise (which was honest) as a
criticism. It just quite literally not what I thought head(array(100, c(25,
2, 2))) would have done based on what head.matrix does is all.
>
> Note however the following historical quirk :
>
> > sapply(setNames(,1:5), function(K) inherits(array(pi, dim=1:K), "array"))
> 1 2 3 4 5
> TRUE FALSE TRUE TRUE TRUE
>
> (Is this something we should consider changing for R 4.0.0 -- to
> have it TRUE also for 2d-arrays aka matrix objects ??)
>
That is pretty odd. IMHO It would be quite nice from a design perspective
to fix that, but I do wonder, as I infer you do as well, how much code it
would break.
Changing this would cause problems in any case where a generic has an array
method but no matrix method, as well as any code that explicitly checks for
inherits from "array" assuming matrices won't return true, correct? My
intuition is that the former would be pretty rare, though it might be a fun
little problem to figure it out. The latter is ...probably also fairly
rare? My intuition on that one is less strong though.
>
> The consequence of that is that
> currently, "often" foo.matrix is just a copy of foo.array in
> the case the latter exists:
> "base" examples: foo in {unique, duplicated, anyDuplicated}.
>
> So I propose you change current head.matrix and tail.matrix to
> head.array and tail.array
> (and then have head.matrix <- head.array etc, at least if the
> above quirk must remain, or remains (which I currently guess to
> be the case)).
>
>
Absolutely, will do. I'm gratified we're going after the more general
approach. Thanks for working with us on this.
Best,
~G
>
> >> x = array(100, c(4, 5, 5))
>
> >> dim(x)
>
> > [1] 4 5 5
>
> >> head(x, 1)
>
> > [1] 100
>
> >> class(head(x))
>
> > [1] "numeric"
>
>
> > (For a 1d array, it does return another 1d array).
>
> > When extending head/tail to understand multiple dimensions as
> discussed in
> > this thread, then, should the behavior for 2+d arrays be explicitly
> > retained, or should head and tail do the analogous thing (with a
> head(<2d
> array> ) behaving the same as head(), which honestly is what I
> > expected to already be happening)?
>
> > Are people using/relying on this behavior in their code, and if so,
> why/for
> > what?
>
> > Even more generally, one way forward is to have the default methods
> check
> > for dimensions, and use length if it is null:
>
> > tail.default <- tail.data.frame <- function(x, n = 6L, ...)
> > {
> > if(any(n == 0))
> > stop("n must be non-zero or unspecified for all dimensions")
> > if(!is.null(dim(x)))
> > dimsx <- dim(x)
> > else
> > dimsx <- length(x)
>
> > ## this returns a list of vectors of indices in each
> > ## dimension, regardless of length of the the n
> > ## argument
> > sel <- lapply(seq_along(dimsx), function(i) {
> > dxi <- dimsx[i]
> > ## select all indices (full dim) if not specified
> > ni <- if(length(n) >= i) n[i] else dxi
> > ## handle negative ns
> > ni <- if (ni < 0L) max(dxi + ni, 0L) else min(ni, dxi)
> > seq.int(to = dxi, length.out = ni)
> > })
> > args <- c(list(x), sel, drop = FALSE)
> > do.call("[", args)
> > }
>
>
> > I think this precludes the need for a separate data.frame method at
> all,
> > actually, though (I would think) tail.data.frame would still be
> defined and
> > exported for backwards compatibility. (the matrix method has some
> extra
> > bits so my current conception of it is still separate, though it
> might not
> > NEED to be).
>
> > The question then b
Re: [Rd] head.matrix can return 1000s of columns -- limit to n or add new argument?
On 10/30/19 04:29, Martin Maechler wrote:
>> Gabriel Becker
>> on Tue, 29 Oct 2019 12:43:15 -0700 writes:
>
> > Hi all,
> > So I've started working on this and I ran into something that I didn't
> > know, namely that for x a multi-dimensional (2+) array, head(x) and
> tail(x)
> > ignore dimension completely, treat x as an atomic vector, and return an
> > (unclassed) atomic vector:
>
> Well, that's (3+), not "2+" .
>
> But I did write (on Sep 17 in this thread!)
>
>> The current source for head() and tail() and all their methods
>> in utils is just 83 lines of code {file utils/R/head.R minus
>> the initial mostly copyright comments}.
>
> and if've ever looked at these few dozen of R code lines, you'll
> have seen that we just added two simple utilities with a few
> reasonable simple methods. To treat non-matrix (i.e. non-2d)
> arrays as vectors, is typically not unreasonable in R, but
> indeed with your proposals (in this thread), such non-2d arrays
> should be treated differently either via new head.array() /
> tail.array() methods ((or -- only if it can be done more nicely -- by
> the default method)).
>
> Note however the following historical quirk :
>
>> sapply(setNames(,1:5), function(K) inherits(array(pi, dim=1:K), "array"))
> 1 2 3 4 5
> TRUE FALSE TRUE TRUE TRUE
>
> (Is this something we should consider changing for R 4.0.0 -- to
> have it TRUE also for 2d-arrays aka matrix objects ??)
That would be awesome! More generally I wonder how feasible it would be
to fix all these inheritance quirks where inherits(x, "something"),
is(x, "something"), and is.something(x) disagree. They've been such a
nuisance for so many years...
Thanks,
H.
>
> The consequence of that is that
> currently, "often" foo.matrix is just a copy of foo.array in
> the case the latter exists:
> "base" examples: foo in {unique, duplicated, anyDuplicated}.
>
> So I propose you change current head.matrix and tail.matrix to
> head.array and tail.array
> (and then have head.matrix <- head.array etc, at least if the
> above quirk must remain, or remains (which I currently guess to
> be the case)).
>
>
> >> x = array(100, c(4, 5, 5))
>
> >> dim(x)
>
> > [1] 4 5 5
>
> >> head(x, 1)
>
> > [1] 100
>
> >> class(head(x))
>
> > [1] "numeric"
>
>
> > (For a 1d array, it does return another 1d array).
>
> > When extending head/tail to understand multiple dimensions as
> discussed in
> > this thread, then, should the behavior for 2+d arrays be explicitly
> > retained, or should head and tail do the analogous thing (with a
> head(<2d
> array> ) behaving the same as head(), which honestly is what I
> > expected to already be happening)?
>
> > Are people using/relying on this behavior in their code, and if so,
> why/for
> > what?
>
> > Even more generally, one way forward is to have the default methods
> check
> > for dimensions, and use length if it is null:
>
> > tail.default <- tail.data.frame <- function(x, n = 6L, ...)
> > {
> > if(any(n == 0))
> > stop("n must be non-zero or unspecified for all dimensions")
> > if(!is.null(dim(x)))
> > dimsx <- dim(x)
> > else
> > dimsx <- length(x)
>
> > ## this returns a list of vectors of indices in each
> > ## dimension, regardless of length of the the n
> > ## argument
> > sel <- lapply(seq_along(dimsx), function(i) {
> > dxi <- dimsx[i]
> > ## select all indices (full dim) if not specified
> > ni <- if(length(n) >= i) n[i] else dxi
> > ## handle negative ns
> > ni <- if (ni < 0L) max(dxi + ni, 0L) else min(ni, dxi)
> > seq.int(to = dxi, length.out = ni)
> > })
> > args <- c(list(x), sel, drop = FALSE)
> > do.call("[", args)
> > }
>
>
> > I think this precludes the need for a separate data.frame method at
> all,
> > actually, though (I would think) tail.data.frame would still be
> defined and
> > exported for backwards compatibility. (the matrix method has some extra
> > bits so my current conception of it is still separate, though it might
> not
> > NEED to be).
>
> > The question then becomes, should head/tail always return something
> with
> > the same dimensionally (number of dims) it got, or should data.frame
> and
> > matrix be special cased in this regard, as they are now?
>
> > What are people's thoughts?
> > ~G
>
> > [[alternative HTML version deleted]]
>
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--
H
Re: [Rd] head.matrix can return 1000s of columns -- limit to n or add new argument?
On Fri, Nov 1, 2019 at 10:02 AM Pages, Herve wrote: > That would be awesome! More generally I wonder how feasible it would be > to fix all these inheritance quirks where inherits(x, "something"), > is(x, "something"), and is.something(x) disagree. They've been such a > nuisance for so many years... This matter was raised in March: https://stat.ethz.ch/pipermail/r-devel/2019-March/077457.html In principle, I agree. However, I'm not sure it's possible without causing compatibility problems. Not to mention all the disagreement about what's the correct approach. And I should probably apologize for incorrectly suggesting that there was a non-backward-compatible design flaw... __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] head.matrix can return 1000s of columns -- limit to n or add new argument?
Hmm, the problem I see here is that these implied classes are all inherently
one-off. We also have
> inherits(matrix(1,1,1),"numeric")
[1] FALSE
> is.numeric(matrix(1,1,1))
[1] TRUE
> inherits(1L,"numeric")
[1] FALSE
> is.numeric(1L)
[1] TRUE
and if we start fixing one, we might need to fix all.
For method dispatch, we do have inheritance, e.g.
> foo.numeric <- function(x) x + 1
> foo <- function(x) UseMethod("foo")
> foo(1)
[1] 2
> foo(1L)
[1] 2
> foo(matrix(1,1,1))
[,1]
[1,]2
> foo.integer <- function(x) x + 2
> foo(1)
[1] 2
> foo(1L)
[1] 3
> foo(matrix(1,1,1))
[,1]
[1,]2
> foo(matrix(1L,1,1))
[,1]
[1,]3
but these are not all automatic: "integer" implies "numeric", but "matrix" does
not imply "numeric", much less "integer".
Also, we seem to have a rule that inherits(x, c) iff c %in% class(x), which
would break -- unless we change class(x) to return the whole set of inherited
classes, which I sense that we'd rather not do
-pd
> On 30 Oct 2019, at 12:29 , Martin Maechler wrote:
>
> Note however the following historical quirk :
>
>> sapply(setNames(,1:5), function(K) inherits(array(pi, dim=1:K), "array"))
>1 2 3 4 5
> TRUE FALSE TRUE TRUE TRUE
>
> (Is this something we should consider changing for R 4.0.0 -- to
> have it TRUE also for 2d-arrays aka matrix objects ??)
--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd@cbs.dk Priv: pda...@gmail.com
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