Stavros Macrakis wrote:
Thanks for the quick fix!
It was quick in R-devel, not so quick in R-patched. I forgot to commit
the change, but someone accidentally ported my NEWS item about it over,
so I thought I really had done it when I looked from another computer
the next day. Then I headed out on the road...
Will commit it to R-patched (from the Vancouver airport) in a few minutes.
Duncan Murdoch
-s
On Fri, May 29, 2009 at 1:02 PM, Duncan Murdoch <murd...@stats.uwo.ca>wrote:
On 5/29/2009 9:28 AM, Duncan Murdoch wrote:
I've moved this to R-devel...
On 5/28/2009 8:17 PM, Stavros Macrakis wrote:
I couldn't get your suggested method to work:
`==.foo` <- function(a,b) unclass(a)==unclass(b)
`>.foo` <- function(a,b) unclass(a) < unclass(b) # invert comparison
is.na.foo <- function(a)is.na(unclass(a))
sort(structure(sample(5),class="foo")) #-> 1:5 -- not reversed
What am I missing?
There are two problems. First, I didn't mention that you need a method
for indexing as well. The code needs to evaluate things like x[i] > x[j],
and by default x[i] will not be of class "foo", so the custom comparison
methods won't be called.
Second, I think there's a bug in the internal code, specifically in
do_rank or orderVector1 in sort.c: orderVector1 ignores the class of x.
do_rank pays attention when breaking ties, so I think this is an oversight.
So I'd say two things should be done:
1. the bug should be fixed. Even if this isn't the most obvious
approach, it should work.
I've now fixed the bug, and clarified the documentation to say
The default method will make use of == and > methods
for the class of x[i] (for integers i), and the
is.na method for the class of x, but might be rather
slow when doing so.
You don't actually need a custom indexing method, you just need to be aware
that it's the class of x[i] that is important for comparisons.
This will make it into R-patched and R-devel.
Duncan Murdoch
2. we should look for ways to make all of this simpler, e.g. allowing a
comparison function to be used.
I'll take on 1, but not 2. It's hard to work out the right place for the
comparison function to appear, and it would require a lot of work to
implement, because all of this stuff (sort, rank, order, xtfrm, sort.int,
etc.) is closely interrelated, some but not all of the functions are S3
generics, some implemented internally, etc. In the end, I'd guess the
results won't be very satisfactory from a performance point of view: all
those calls out to R to do the comparisons are going to be really slow.
I think your advice to use order() with multiple keys is likely to be much
faster in most instances. It's just a better approach in R.
Duncan Murdoch
-s
On Thu, May 28, 2009 at 5:48 PM, Duncan Murdoch <murd...@stats.uwo.ca
wrote:
On 28/05/2009 5:34 PM, Steve Jaffe wrote:
Sounds simple but haven't been able to find it in docs: is it possible
to
sort a vector using a user-defined comparison function? Seems it must
be,
but "sort" doesn't seem to provide that option, nor does "order" sfaics
You put a class on the vector (e.g. using class(x) <- "myvector"), then
define a conversion to numeric (e.g. xtfrm.myvector) or actual
comparison
methods (you'll need ==.myvector, >.myvector, and is.na.myvector).
Duncan Murdoch
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