Intersection of two sets of intervals
Stavros, you are quite correct -- I discovered that the hard way a little while ago when testing my two-line solution. Use of pmin/pmax don't handle, for instance, cases where more than one interval in one set is wholly contained by an interval in the other. (I have a mis-posted msg awaiting moderator approval in R-help with a concrete example.) Your tip to check out the intervals pkg looks promising. FYI, there the general intersection is computed as the complement of the union of the complements, i.e. A*B = (A'+B')' , aka DeMorgan. Thanks for the help, -tom
On 4/15/2009 11:27 AM, Stavros Macrakis wrote:
I can see how pmax/pmin would easily allow the intersection of
corresponding elements of two sequences of intervals, but I don't see
how they help in intersecting two *sets* of intervals, which was the
original problem statement.
-s
On Wed, Apr 15, 2009 at 9:14 AM, ONKELINX, Thierry
<Thierry.ONKELINX at inbo.be> wrote:
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 -- Thomas Meyer
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