Algorithms for colourful simplicial depth and median in the plane

Author: 
Date created: 
2017-04-07
Identifier: 
etd10062
Keywords: 
Computational geometry
Data depth
Colourful simplicial depth
Bivariate medians
Topological sweep
Abstract: 

The colourful simplicial depth (CSD) of a point x in R^2 relative to a configuration P=(P^1, P^2, ..., P^k) of n points in k colour classes is exactly the number of closed simplices (triangles) with vertices from 3 different colour classes that contain x in their convex hull. We consider the problems of efficiently computing the colourful simplicial depth of a point x, and of finding a point in R^2, called a median, that maximizes colourful simplicial depth. For computing the colourful simplicial depth of x, our algorithm runs in time O(n log(n) + kn) in general, and O(kn) if the points are sorted around x. For finding the colourful median, we get a time of O(n^4). For comparison, the running times of the best known algorithm for the monochrome version of these problems are O(n log(n)) in general, improving to O(n) if the points are sorted around x for monochrome depth, and O(n^4) for finding a monochrome median.

Document type: 
Thesis
Rights: 
This thesis may be printed or downloaded for non-commercial research and scholarly purposes. Copyright remains with the author.
File(s): 
Senior supervisor: 
Tamon Stephen
Department: 
Science: Department of Mathematics
Thesis type: 
(Thesis) M.Sc.
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