Hi all, Would anyone be interested in reviewing a patch to make the set operations (union, intersect, setdiff, setequal, is.element) generic? Thanks, Hadley
Chief Scientist, RStudio http://had.co.nz/
Set operation generics
4 messages · Hadley Wickham, Hervé Pagès
Hi Hadley,
On 10/21/2013 10:51 AM, Hadley Wickham wrote:
Hi all, Would anyone be interested in reviewing a patch to make the set operations (union, intersect, setdiff, setequal, is.element) generic?
S3 generics, S4 generics, or primitives?
Since they are binary operations, sounds like supporting multiple
dispatch would be a plus.
Note that all those things heavily rely on match() behind the scene.
If match() itself was an S4 generic (or a primitive like c() and [)
then union(), intersect(), setdiff(), is.element() could be defined
with something like:
union <- function(x, y)
{
xy <- c(x, y)
sm <- match(xy, xy)
xy[sm == seq_along(sm)]
}
intersect <- function(x, y)
{
sm <- match(x, x)
x <- x[sm == seq_along(sm)]
m <- match(x, y)
x[!is.na(m)]
}
setequal <- function(x, y)
{
!(anyNA(match(x, y)) || anyNA(match(x, y)))
}
and as long as your objects support [, c(), and match(), then the set
operations will work out-of-the-box on them. Note that you would also
get %in% for free.
There might be some rare situations where it might still be useful
that the set operations are generic functions but I see a lot more
value in making match() itself a generic (which doesn't exclude also
making the set operations generic).
For the record, match(), union(), intersect(), and setdiff() are S4
generics in the BiocGenerics package. But there is no doubt it would
be a better/cleaner situation if base::match() itself was an S4 generic
or primitive.
My 2 cents,
Cheers,
H.
Thanks, Hadley
Herv? Pag?s Program in Computational Biology Division of Public Health Sciences Fred Hutchinson Cancer Research Center 1100 Fairview Ave. N, M1-B514 P.O. Box 19024 Seattle, WA 98109-1024 E-mail: hpages at fhcrc.org Phone: (206) 667-5791 Fax: (206) 667-1319
Would anyone be interested in reviewing a patch to make the set operations (union, intersect, setdiff, setequal, is.element) generic?
S3 generics, S4 generics, or primitives?
I would expect S3. Can you even have an S4 generic in the base package? (i.e. before the methods package is loaded)
Note that all those things heavily rely on match() behind the scene.
If match() itself was an S4 generic (or a primitive like c() and [)
then union(), intersect(), setdiff(), is.element() could be defined
with something like:
union <- function(x, y)
{
xy <- c(x, y)
sm <- match(xy, xy)
xy[sm == seq_along(sm)]
}
intersect <- function(x, y)
{
sm <- match(x, x)
x <- x[sm == seq_along(sm)]
m <- match(x, y)
x[!is.na(m)]
}
setequal <- function(x, y)
{
!(anyNA(match(x, y)) || anyNA(match(x, y)))
}
Although I suspect R-core would prefer a minimal change where it's easier to see that existing behaviour is preserved.
For the record, match(), union(), intersect(), and setdiff() are S4 generics in the BiocGenerics package. But there is no doubt it would be a better/cleaner situation if base::match() itself was an S4 generic or primitive.
By primitive, you mean internal generic? Hadley
Chief Scientist, RStudio http://had.co.nz/
Hi Hadley,
On 10/22/2013 07:54 AM, Hadley Wickham wrote:
Would anyone be interested in reviewing a patch to make the set operations (union, intersect, setdiff, setequal, is.element) generic?
S3 generics, S4 generics, or primitives?
I would expect S3. Can you even have an S4 generic in the base package? (i.e. before the methods package is loaded)
Probably not. But the patch could be trying to put them in stats4.
Note that all those things heavily rely on match() behind the scene.
If match() itself was an S4 generic (or a primitive like c() and [)
then union(), intersect(), setdiff(), is.element() could be defined
with something like:
union <- function(x, y)
{
xy <- c(x, y)
sm <- match(xy, xy)
xy[sm == seq_along(sm)]
}
intersect <- function(x, y)
{
sm <- match(x, x)
x <- x[sm == seq_along(sm)]
m <- match(x, y)
x[!is.na(m)]
}
setequal <- function(x, y)
{
!(anyNA(match(x, y)) || anyNA(match(x, y)))
}
Although I suspect R-core would prefer a minimal change where it's easier to see that existing behaviour is preserved.
For the record, match(), union(), intersect(), and setdiff() are S4 generics in the BiocGenerics package. But there is no doubt it would be a better/cleaner situation if base::match() itself was an S4 generic or primitive.
By primitive, you mean internal generic?
Yes. Thanks, H.
Hadley
Herv? Pag?s Program in Computational Biology Division of Public Health Sciences Fred Hutchinson Cancer Research Center 1100 Fairview Ave. N, M1-B514 P.O. Box 19024 Seattle, WA 98109-1024 E-mail: hpages at fhcrc.org Phone: (206) 667-5791 Fax: (206) 667-1319