[Rd] c.factor

[Roger Bivand]

On Wed, 15 Nov 2006, Barry Rowlingson wrote:

> 
> > 
> > It does not remove names in Splus either, just all
> > other attributes.  I see c() used in several Splus
> > functions as a way to convert a matrix into a vector
> > (by removing the .Dims and .Dimnames attributes).
> > 
> 
>   I dont see the logic in certain attribute names (?attr lists 'class', 
> 'comment', 'dim', 'dimnames', 'names', 'row.names' and 'tsp') being 
> 'special'. Why are matrices  vectors with some 'magic' attribute 'dim', 
> and possibly some non-magic attributes like 'umbongo' and 'fnord'? I'd 
> have the dim (and other essential properties of data structures) more 
> tightly bound to the data. attr(M,'dim')=NULL seems a very odd way of 
> turning a matrix into a vector.
> 
>   If I was the R bdfl[1] I'd deprecate using 'attr' to access these 
> aspects of data objects and insist on using "dim(M)" or 
> "row.names(M)=foo".

I have a less than vague feeling that you as bdfl are describing new-style 
classes:

library(Matrix)
x <- Matrix(1:6, nrow=2, ncol=3)
getSlots(class(x))
slot(x, "Dim")
slot(x, "Dim") <- NULL

but perhaps unfortunately:

slot(x, "Dim") <- as.integer(c(0,0,0))

works! Maybe not quite what was intended?

> Then I can use 'attr' for any old annotations, for 
> example in my light bulb brightness study I could do:
> 
>   sample1 = c(4.2,4.5,4.8,4.1)
>   attr(sample1,'dim') = TRUE
> 
>   sample2 = c(5.6,5.8,6.7,6.5,9.3)
>   attr(sample2,'dim') = FALSE
> 
> Barry
> 
> [1] http://en.wikipedia.org/wiki/Benevolent_Dictator_for_Life
> 
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> 

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no