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I have a series of n points in d-dimensional continuous space. I want to find a series of hyperplanes such that k points are below the hyperplane and that the set of k points below each hyperplane is a unique set. It does not matter what the hyperplane is (e.g. if it connects d points or if it is another hyperplane not intersecting any points). I can discretise the space if it helps. "below" is defined as the negative direction for the first dimension.

The way I have approached is to try all hyperplanes defined by all sets of d points, project each point on to this hyperplane, and test if the projection is above the point. This results in n^(d+1) complexity.

Is there a better way? What is it?

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    $\begingroup$ Why do you want to compute this ? $\endgroup$
    – Suresh Venkat
    Jun 11, 2014 at 11:41
  • $\begingroup$ It's a component of an algorithm for work $\endgroup$
    – Jayen
    Jun 12, 2014 at 0:26

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If I understand well, you are interested in the $k$-set problem: http://en.wikipedia.org/wiki/K-set_(geometry)

In general their number can be $O(n^{\lfloor d/2\rfloor}k^{\lceil d/2\rceil})$ and though I could not find references now, I think you can also compute them in about this much time.

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  • $\begingroup$ My fear was that this question was a homework question: that's why I asked for the motivation . $\endgroup$
    – Suresh Venkat
    Jun 11, 2014 at 22:11
  • $\begingroup$ Thanks. That's what I was looking for. Didn't know there was a similar problem with a name. I thought about something like Edelsbrunner and Welzl (1986) viewed in terms of k-sets of point sets but couldn't formalise it. Time to learn about bitangents! $\endgroup$
    – Jayen
    Jun 12, 2014 at 0:28

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