"Theodor Zouk" <rebet4@hotmail.com> wrote in message <j8o7c9$m9m$1@newscl01ah.mathworks.com>...
> Hello!
> Im having a problem getting the indices (integers) from overlapping intervals. Let me explain:
>
> let's say for instance that I have some intervals belonging to say
>
> set A:
> [1,3]
> [5,8]
> [11,12]
>
> set B:
> [4,6]
> [8,10]
>
...... Im wondering if there exists some solution (maybe mathematical formula) to find the indices(integers) where intervals overlaps based only on the start and end values.
         
If the numbers of intervals in each set are not large or if time of execution is not important, you could always use the "brute" force method of comparing each interval of one set with each interval of the second set. If each of the two sets of intervals consist of mutually disjoint intervals, then the results of this procedure would also have disjoint intervals. Each individual test might look something like this. Let [a,b] be an interval in set A and [c,d] an interval in B. Whenever max(a,c) <= min(b,d) then add [max(a,c),min(b,d)] to the list of common starting and stopping "indices". Either way, move on to the next pair.
If each set has mutually disjoint intervals and these have been arranged in ascending order in each set (as in your example,) you could do a kind of "merge", commencing at the beginning of each set, in which a pair of intervals from the two respective sets are "compared". If by the test in the first paragraph above there is a nonempty intersection, add it to your list. Whether or not there is such an intersection, you advance to the next interval of the set that had the smallest upper bound. The resulting list will also have disjoint, ascending intervals. This procedure would presumably be much faster than the brute force method above.
Roger Stafford
