Re: [Rd] x <- 1:2; dim(x) <- 2? A vector or not?

Tony Plate Fri, 16 Jan 2009 12:11:51 -0800

Martin Maechler wrote:

"PatB" == Patrick Burns <pbu...@pburns.seanet.com>
    on Tue, 13 Jan 2009 17:00:40 +0000 writes:


    PatB> Henrik Bengtsson wrote:
    >> Hi.

>>>> On Mon, Jan 12, 2009 at 11:58 PM, Prof Brian Ripley

    >> <rip...@stats.ox.ac.uk> wrote:

>>>>> What you have is a one-dimensional array: they crop up

    >>> in R most often from table() in my experience.

>>>>>>>>>> f <- table(rpois(100, 4)) str(f)>>>>>>> 'table' int [, 1:10] 2 6 18 21 13 16 13 4 3 4 - attr(*,

    >>> "dimnames")=List of 1 ..$ : chr [1:10] "0" "1" "2" "3"
    >>> ...

>>>>>> and yes, f is an atmoic vector and yes, str()'s notation

    >>> is confusing here but if it did [1:10] you would not
    >>> know it was an array.  I recall discussing this with
    >>> Martin Maechler (str's author) last century, and I've
    >>> just checked that R 2.0.0 did the same.

>>>>>> The place in which one-dimensional arrays differ from

    >>> normal vectors is how names are handled: notice that my
    >>> example has dimnames not names, and ?names says

>>>>>> For a one-dimensional array the 'names' attribute really

    >>> is 'dimnames[[1]]'.

>>>>>>> Thanks for this explanation. One could then argue that

    >> [1:10,] is somewhat better than [,1:10], but that is just polish.

yes.  And honestly I don't remember anymore why I chose the
"[,1:n]" notation.  It definitely was there already before R
came into existence, as  S  also has had one-dimensional arrays,
and I programmed the first version of str() in 1990.

    PatB> Perhaps it could be:

    PatB> [1:10(,)]

    PatB> That is weird enough that it should not lead people to
    PatB> believe that it is a matrix.  But might prompt them a
    PatB> bit in that direction.

Well, str() was always aimed a bit at experienced S (and R)
users, and I had always aimed somewhat to keep it's output
"compact".  I'm quite astonished that the OP didn't know about
1D arrays in spite of the many years he's been using R.
Would a wierd solution like the above have helped?

At the moment, I'd tend to keep it "as is" if only just for
historical reminescence, but I can be convinced to change the

current "tendency" ...Martin Maechler, ETH Zurich

What about just including "(1d-array)", something like this
> str(f)
'table' int [1:10](1d array) 5 5 9 23 26 16 9 4 2 1
- attr(*, "dimnames")=List of 1
 ..$ : chr [1:10] "0" "1" "2" "3" ...
>
only 9 extra characters for a rare case, and much, much less cryptic?

-- Tony Plate

    PatB> Patrick Burns patr...@burns-stat.com +44 (0)20 8525
    PatB> 0696 http://www.burns-stat.com (home of "The R
    PatB> Inferno" and "A Guide for the Unwilling S User")
    >> /Henrik
>>>>>>> I think these days we have enough internal glue in place
    >>> that an end user would not notice the difference (but
    >>> those working at C level with R objects may need to
    >>> know).
>>>>>> On Mon, 12 Jan 2009, Henrik Bengtsson wrote:>>>>>>>>>> Ran into the follow intermediate case in an external
    >>>> package (w/ recent R v2.8.1 patched and R v2.9.0
    >>>> devel):
>>>>>>>>>>>>> x <- 1:2 dim(x) <- 2 dim(x)>>>>>>>>> [1] 2>>>>>>>>> x>>>>>>>>> [1] 1 2>>>>>>>>> str(x)>>>>>>>>> int [, 1:2] 1 2>>>>>>>>> nrow(x)>>>>>>>>> [1] 2>>>>>>>>> ncol(x)>>>>>>>>> [1] NA>>>>>>>>> is.vector(x)>>>>>>>>> [1] FALSE>>>>>>>>> is.matrix(x)>>>>>>>>> [1] FALSE>>>>>>>>> is.array(x)>>>>>>>>> [1] TRUE>>>>>>>>> x[1]>>>>>>>>> [1] 1>>>>>>>>> x[,1]>>>>>>>>> Error in x[, 1] : incorrect number of dimensions>>>>>>>>> x[1,]>>>>>>>>> Error in x[1, ] : incorrect number of dimensions>>>>>>>> Is str() treating single-dimension arrays incorrectly?>>>>>>>> What does it mean to have a single dimension this way?
    >>>> Should it equal a vector?  I am aware of "is.vector
    >>>> returns FALSE if x has any attributes except names".
>>>>>>>> /Henrik>>>>>>>> ______________________________________________
    >>>> R-devel@r-project.org mailing list
    >>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>>>>>>>>>> --
Brian D. Ripley, rip...@stats.ox.ac.uk Professor of Applied
    >>> Statistics, http://www.stats.ox.ac.uk/~ripley/
    >>> University of Oxford, Tel: +44 1865 272861 (self) 1
    >>> South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG,
    >>> UK Fax: +44 1865 272595
>>>>>> ______________________________________________
    >>> R-devel@r-project.org mailing list
    >>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>>>>>>>
______________________________________________
    >> R-devel@r-project.org mailing list
    >> https://stat.ethz.ch/mailman/listinfo/r-devel
>>>>>>
______________________________________________
    PatB> R-devel@r-project.org mailing list
    PatB> https://stat.ethz.ch/mailman/listinfo/r-devel

______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel


______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel

Re: [Rd] x <- 1:2; dim(x) <- 2? A vector or not?

Reply via email to