Intersection of two sets of intervals

Not of the self but still not complicated:

list1 <- data.frame(open=c(1,5), close=c(2,10))
list2 <- data.frame(open=c(1.5,3), close=c(2.5,10))

Intersec <- data.frame(Open = pmax(list1$open, list2$open), Close =
pmin(list1$close, list2$close))
Intersec[Intersec$Open > Intersec$Close, ] <- NA
Intersec

HTH,

Thierry

------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium 
tel. + 32 54/436 185
Thierry.Onkelinx at inbo.be 
www.inbo.be 

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to
say what the experiment died of.
~ Sir Ronald Aylmer Fisher

The plural of anecdote is not data.
~ Roger Brinner

The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of
data.
~ John Tukey

-----Oorspronkelijk bericht-----
Van: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
Namens Thomas Meyer
Verzonden: woensdag 15 april 2009 14:59
Aan: r-help at r-project.org
Onderwerp: [R] Intersection of two sets of intervals

Hi,

Algorithm question: I have two sets of "intervals", where an interval is

an ordered pair [a,b] of two numbers. Is there an efficient way in R to 
generate the intersection of two lists of same?

For concreteness: I'm representing a set of intervals with a data.frame:

 > list1 = as.data.frame(list(open=c(1,5), close=c(2,10)))
 > list1

   open close
1    1     2
2    5    10

 > list2 = as.data.frame(list(open=c(1.5,3), close=c(2.5,10)))
 > list2

   open close
1  1.5   2.5
2  3.0  10.0

How do I get the intersection which would be something like:
   open close
1  1.5   2.0
2  5.0  10.0

I wonder if there's some ready-built functionality that might help me 
out. I'm new to R and am still learning to vectorize my code and my 
thinking. Or maybe there's a package for interval arithmetic that I can 
just pull off the shelf.

Thanks,

-tom