R help - Dec 2007 - Dimension of a vector

Consider the following:
> A <- 1:10
> A
 [1]  1  2  3  4  5  6  7  8  9 10
> dim(A)
NULL
> dim(A) <- c(2,5)
> A
     [,1] [,2] [,3] [,4] [,5]
[1,]    1    3    5    7    9
[2,]    2    4    6    8   10
> dim(A)
[1] 2 5
> dim(A) <- 10
> A
 [1]  1  2  3  4  5  6  7  8  9 10
> dim(A)
[1] 10

Would it not make sense to have dim(A) = length(A) for all vectors?

Murray
-- 
Dr Murray Jorgensen      http://www.stats.waikato.ac.nz/Staff/maj.html
Department of Statistics, University of Waikato, Hamilton, New Zealand
Email: maj at waikato.ac.nz                                Fax 7 838 4155
Phone  +64 7 838 4773 wk    Home +64 7 825 0441    Mobile 021 1395 862

In R, vectors don't have dimensions, arrays do.
> x <- c(1, 4, 5)
> class(x)
[1] "numeric"
> y <- array(x)
> class(y)
[1] "array"
> dim(x)
NULL
> dim(y)
[1] 3

On Dec 4, 2007 7:35 PM,  <maj at stats.waikato.ac.nz>
wrote:
> Consider the following:
> > A <- 1:10
> > A
>  [1]  1  2  3  4  5  6  7  8  9 10
> > dim(A)
> NULL
> > dim(A) <- c(2,5)
> > A
>     [,1] [,2] [,3] [,4] [,5]
> [1,]    1    3    5    7    9
> [2,]    2    4    6    8   10
> > dim(A)
> [1] 2 5
> > dim(A) <- 10
> > A
>  [1]  1  2  3  4  5  6  7  8  9 10
> > dim(A)
> [1] 10
>
> Would it not make sense to have dim(A) = length(A) for all vectors?
>
> Murray
> --
> Dr Murray Jorgensen      http://www.stats.waikato.ac.nz/Staff/maj.html
> Department of Statistics, University of Waikato, Hamilton, New Zealand
> Email: maj at waikato.ac.nz                                Fax 7 838 4155
> Phone  +64 7 838 4773 wk    Home +64 7 825 0441    Mobile 021 1395 862
>
> ______________________________________________
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

On Wed, 5 Dec 2007, maj at stats.waikato.ac.nz wrote:
> Consider the following:
>> A <- 1:10
>> A
> [1]  1  2  3  4  5  6  7  8  9 10
>> dim(A)
> NULL
>> dim(A) <- c(2,5)
>> A
>     [,1] [,2] [,3] [,4] [,5]
> [1,]    1    3    5    7    9
> [2,]    2    4    6    8   10
>> dim(A)
> [1] 2 5
>> dim(A) <- 10
>> A
> [1]  1  2  3  4  5  6  7  8  9 10
>> dim(A)
> [1] 10
>
> Would it not make sense to have dim(A) = length(A) for all vectors?
No.  A one-dimensional array and a vector are not the same thing.
There are subtle differences, such as what names() means (see ?names).

That a 1D array and a vector _print_ in the same way does occasionally 
lead to confusion, but then you also cannot tell from your printout that A 
has type "integer" and not "double".

-- 
Brian D. Ripley,                  ripley at 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