There is a description in the 'Blue Book' (Becker et al, 1988) of when
attributes are supposed to be preserved, and R mostly conforms to it.
This is discussed somewhere relevant in the R documentation: I would
have to search for exactly where, so I leave that to you.
On Wed, 19 Oct 2011, John C Nash wrote:
I've been trying to prepare some wrappers for optimization objective functions
and
gradients that use try() to check for computable functions. I'm also trying to
do scaling
as per optim() so that a number of methods that are available on CRAN and
R-Forge can use
parameter and function scaling. This got me into minor trouble when I scaled a
gradient or
Hessian and the "inadmissible" attribute I had created suddenly disappeared.
When I
discovered why -- that some operations don't preserve attributes -- I started
to look for
a list of which ops preserve attributes and which don't. The code snippet below
shows that
matrix multiplication (%*%) does not, while multiplication by a vector (simple
*) does.
I'm not really surprised that some ops don't preserve attributes, particularly
those that
are binary like multiplication, but it might be nice to know which operations
and special
functions do so.
rm(list=ls())
m<-matrix(1:4,nrow=2, ncol=2)
print(m)
attributes(m)
attr(m,"check")<-"***"
attributes(m)
bigm<-10*m
str(bigm)
bigm1<-diag(c(1,1))%*%m
str(bigm1)
bigm1<-c(1,2)*m
str(bigm1)
print(bigm1)
arraym<-as.array(m)
str(arraym)
tanm<-tan(m)
str(tanm)
Best,
John Nash
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Brian D. Ripley, rip...@stats.ox.ac.uk
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