Near-Optimal Explainable $k$-Means for All Dimensions
- URL: http://arxiv.org/abs/2106.15566v1
- Date: Tue, 29 Jun 2021 16:59:03 GMT
- Title: Near-Optimal Explainable $k$-Means for All Dimensions
- Authors: Moses Charikar, Lunjia Hu
- Abstract summary: We show an efficient algorithm that finds an explainable clustering whose $k$-means cost is at most $k1 - 2/dmathrmpoly(dlog k)$.
We get an improved bound of $k1 - 2/dmathrmpolylog(k)$, which we show is optimal for every choice of $k,dge 2$ up to a poly-logarithmic factor in $k$.
- Score: 13.673697350508965
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: Many clustering algorithms are guided by certain cost functions such as the
widely-used $k$-means cost. These algorithms divide data points into clusters
with often complicated boundaries, creating difficulties in explaining the
clustering decision. In a recent work, Dasgupta, Frost, Moshkovitz, and
Rashtchian (ICML'20) introduced explainable clustering, where the cluster
boundaries are axis-parallel hyperplanes and the clustering is obtained by
applying a decision tree to the data. The central question here is: how much
does the explainability constraint increase the value of the cost function?
Given $d$-dimensional data points, we show an efficient algorithm that finds
an explainable clustering whose $k$-means cost is at most $k^{1 -
2/d}\mathrm{poly}(d\log k)$ times the minimum cost achievable by a clustering
without the explainability constraint, assuming $k,d\ge 2$. Combining this with
an independent work by Makarychev and Shan (ICML'21), we get an improved bound
of $k^{1 - 2/d}\mathrm{polylog}(k)$, which we show is optimal for every choice
of $k,d\ge 2$ up to a poly-logarithmic factor in $k$. For $d = 2$ in
particular, we show an $O(\log k\log\log k)$ bound, improving exponentially
over the previous best bound of $\widetilde O(k)$.
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