[Rd] proposal to make loadings() generic in R-devel

[Paul Gilbert]

I propose that loadings() be made generic in R-devel with definition

    loadings <- function(x, ...) UseMethod("loadings")

    loadings.default <- function(x, ...) x$loadings

The default is the current definition of loadings with the ... argument 
added.

The current definition is not specific about the returned value, though 
$loadings may usually be a matrix. I'm not sure what would be broken if 
a more strict definition of the return value is enforced. For my 
purposes a matrix is fine, but I am not sure that there is a benefit 
from imposing that the returned value must be a matrix, so I suggest 
sticking with the current non-specific structure for the return value. 
(For piecewise linear or other non-linear analysis there may be good 
reasons to allow more general structures for the loadings.)

Paul Gilbert