It returns a list with athe class attribut set to "by", just use:
x <- by(.....)
unclass(x)
Uwe Ligges
On 14.09.2010 00:11, Seb wrote:
Hi,
I noticed that by() returns an object of class 'by', regardless of what
its argument 'simplify' is. ?by says that it always returns a list if
simplify=FALSE, yet by.data.frame shows:
---<--------------------cut here---------------start------------------->---
function (data, INDICES, FUN, ..., simplify = TRUE)
{
if (!is.list(INDICES)) {
IND<- vector("list", 1L)
IND[[1L]]<- INDICES
names(IND)<- deparse(substitute(INDICES))[1L]
}
else IND<- INDICES
FUNx<- function(x) FUN(data[x, , drop = FALSE], ...)
nd<- nrow(data)
ans<- eval(substitute(tapply(1L:nd, IND, FUNx, simplify = simplify)),
data)
attr(ans, "call")<- match.call()
class(ans)<- "by"
ans
}
<environment: namespace:base>
---<--------------------cut here---------------end--------------------->---
One could force a list by wrapping it around an lapply(by.object, "["),
but this is not possible if the object contains S4 objects. How does
one force a list in those cases?
Cheers,
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