R devel - Dec 2004 - is.vector(...) <-> is(..., "vector")

Hello,

Is it intended that is.vector(...) and is(..., "vector")
do not always give identical results?

is.vector() works as documented ('is.vector' returns
'FALSE' if 'x' has any attributes except names.)
Thus,

A <- array(1:2, 1:2)
M <- diag(2)

is.vector(M) # FALSE, as documented
# and
is.vector(A) # FALSE, as documented

# however
is(M, "vector") # TRUE
is(A, "vector") # TRUE

# which is also correct, since
extends("matrix", "vector")
extends("array", "vector")

I'm working with R Version 2.0.1 Patched (2004-12-09)
on Windows 2000.

Thanks, for any comments!
Matthias

On Thu, 30 Dec 2004 Matthias.Kohl@uni-bayreuth.de wrote:
> Is it intended that is.vector(...) and is(..., "vector")
> do not always give identical results?
Yes.  What makes you think they are anything to so with each other?
The S4 class "vector" is quite distinct from the usage in base R.
> is.vector() works as documented ('is.vector' returns
> 'FALSE' if 'x' has any attributes except names.)
> Thus,
>
> A <- array(1:2, 1:2)
> M <- diag(2)
>
> is.vector(M) # FALSE, as documented
> # and
> is.vector(A) # FALSE, as documented
>
> # however
> is(M, "vector") # TRUE
> is(A, "vector") # TRUE
>
> # which is also correct, since
> extends("matrix", "vector")
> extends("array", "vector")
>
> I'm working with R Version 2.0.1 Patched (2004-12-09)
> on Windows 2000.
-- 
Brian D. Ripley,                  ripley@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

On Thu, 30 Dec 2004 Matthias.Kohl@uni-bayreuth.de wrote:
> Hello,
>
> Is it intended that is.vector(...) and is(..., "vector")
> do not always give identical results?
Yes. They both work as documented, as you note below. People have often 
pointed out that is.vector is a slightly misleading name, and it might 
have been better if that function had been called something like 
is.bare.vector() back in the Disco Age when it was created. But it wasn't.

 	-thomas
> is.vector() works as documented ('is.vector' returns
> 'FALSE' if 'x' has any attributes except names.)
> Thus,
>
> A <- array(1:2, 1:2)
> M <- diag(2)
>
> is.vector(M) # FALSE, as documented
> # and
> is.vector(A) # FALSE, as documented
>
> # however
> is(M, "vector") # TRUE
> is(A, "vector") # TRUE
>
> # which is also correct, since
> extends("matrix", "vector")
> extends("array", "vector")
>
> I'm working with R Version 2.0.1 Patched (2004-12-09)
> on Windows 2000.
>
> Thanks, for any comments!
> Matthias
>
> ______________________________________________
> R-devel@stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>
Thomas Lumley			Assoc. Professor, Biostatistics
tlumley@u.washington.edu	University of Washington, Seattle