drop(x)
x is an object with a dim attribute
(e.g. a matrix or array), then drop, returns
an object like x, but with any extents of length
one removed. Any accompanying dimnames attribute
is adjusted and returned with x.
Array subsetting typically performs this reduction,
but sometimes it is useful to invoke drop directly.
drop1 which is used for dropping terms in models.dim(drop(array(1:12, dim=c(1,3,1,1,2,1,2))))# = 3 2 2