[Rd] diff(<ts-matrix>), Ops.ts -- R Bugzilla PR#18972

[Martin Maechler]

>>>>> Suharto Anggono Suharto Anggono 
>>>>>     on Fri, 27 Mar 2026 06:50:52 +0000 (UTC) writes:

    > To have usual storage mode of the result and for error if e1 and e2 are matrices with different number of columns, 'Ops.ts' could still use
    > NextMethod(.Generic)
    > even if e1 and e2 are not overlapping and just change e1 and e2.

    > if(is.null(e12))# if e1 or e2 is matrix but e1 & e2 are not overlapping, e12 is NULL ..
    >    return(if(is.matrix(e1))      e1[0, , drop=FALSE]
    >           else if(is.matrix(e2)) e2[0, , drop=FALSE]
    >    ## else NULL ( == e12 )
    >    )
    > e1 <- if(is.matrix(e1)) e12[, 1L:nc1 , drop = FALSE] else e12[, 1]
    > e2 <- if(is.matrix(e2)) e12[, nc1 + (1L:nc2), drop = FALSE] else e12[, nc1 + 1]

    > could become

    > if(is.null(e12)) {# if e1 & e2 are not overlapping, e12 is NULL ..
    > e1 <- if(is.matrix(e1)) e1[0, , drop = FALSE] else e1[0]
    > e2 <- if(is.matrix(e2)) e2[0, , drop = FALSE] else e2[0]
    > } else {
    > e1 <- if(is.matrix(e1)) e12[, 1L:nc1 , drop = FALSE] else e12[, 1]
    > e2 <- if(is.matrix(e2)) e12[, nc1 + (1L:nc2), drop = FALSE] else e12[, nc1 + 1]
    > }

You are right.  It's better to be more consistent than a tiny
bit faster.
===> committed in svn r89843   --- will also port to R 4.6.0 alpha

Martin

    > _______
    > On Wednesday, 4 March 2026 at 06:57:51 pm GMT+7, Martin Maechler <maechler using stat.math.ethz.ch> wrote:


>>>>> Martin Maechler
    >>>>>> on Wed, 4 Mar 2026 12:42:20 +0100 writes:

>>>>> Suharto Anggono Suharto Anggono
    >>>>>> on Wed, 4 Mar 2026 06:05:18 +0000 (UTC) writes:

    >     >> Then, please announce the change in NEWS. For example:
    >     >> The result of arithmetic and comparison operations of non-overlapping "ts" objects where either is a matrix is now a matrix.

    >     >> It seems that the statement "diff(<ts-matrix>) remains matrix, even when it has length zero" was meant for the change to 'Ops.ts'. But the wording is about diff(<ts-matrix>), which is included in the previous statement.

    >     >> But I've just realized this :

    >     >> Suppose that
    >     >> x <- ts(0)

    >     >> With the change, x - lag(x, -1) and x == lag(x, -1) are NULL.
    >     >> In R 4.5.2, x - lag(x, -1) is integer(0) and x == lag(x, -1) is logical(0).

    >     > Indeed, so we may even have to change R-devel further (for this
    >     > rare boundary case).

    >     > But the R 4.5.2  x - lag(x, -1)  giving integer(0)  is only somewhat better than
    >     > giving NULL  when in principle the "truly correct" answer should
    >     > be double(0) and we'd rather get that right in R-devel.

    > ==> So, we should probably reopen R Bugzilla item PR#18972, at
    ---> https://bugs.r-project.org/show_bug.cgi?id=18972

    > Martin