Genieclust Python Package (under development)

The Genie+ Clustering Algorithm

Author: Marek Gagolewski

The time needed to apply a hierarchical clustering algorithm is most often dominated by the number of computations of a pairwise dissimilarity measure. Such a constraint, for larger data sets, puts at a disadvantage the use of all the classical linkage criteria but the single linkage one. However, it is known that the single linkage clustering algorithm is very sensitive to outliers, produces highly skewed dendrograms, and therefore usually does not reflect the true underlying data structure - unless the clusters are well-separated.

To overcome its limitations, we proposed a new hierarchical clustering linkage criterion called Genie. Namely, our algorithm links two clusters in such a way that a chosen economic inequity measure (here, the Gini index) of the cluster sizes does not increase drastically above a given threshold.

Benchmarks indicate a high practical usefulness of the introduced method: it most often outperforms the Ward or average linkage, k-means, spectral clustering, DBSCAN, Birch, and others in terms of the clustering quality while retaining the single linkage speed. The algorithm is easily parallelizable and thus may be run on multiple threads to speed up its execution further on. Its memory overhead is small: there is no need to precompute the complete distance matrix to perform the computations in order to obtain a desired clustering.

See: Gagolewski M., Bartoszuk M., Cena A., Genie: A new, fast, and outlier-resistant hierarchical clustering algorithm, Information Sciences 363, 2016, pp. 8-23. doi:10.1016/j.ins.2016.05.003

This is a new, faster and even more robust implementation of the original algorithm available on CRAN, see R package genie.

Package Features

• The Genie+ algorithm (using a scikit-learn-like interface), together with a robustified version of HDBSCAN*
• DisjointSets data structure (with extensions)
• Various inequity measures (the Gini index, the Bonferroni index, etc.)
• Functions to compute partition similarity measures (the Rand, adjusted Rand, Fowlkes-Mallows, and adjusted Fowlkes-Mallows index)
• An implementation of the Prim algorithm to compute the minimum spanning tree (@TODO@ parallelized, requiring O(n**2) time and O(n) memory)
• Various plotting functions

Installation

The package requires Python 3.6+ together with sklearn, numpy, scipy, matplotlib, and cython.

Via pip:

# @TODO@ - not yet on PyPI

The most recent development version:

git clone https://github.com/gagolews/genieclust.git
cd genieclust
python setup.py build_ext --inplace
python setup.py install --user

Examples

• The Genie Algorithm - basic use
• The Genie Algorithm with Noise Points Detection

License

This package is licensed under the BSD 3-Clause "New" or "Revised" License.

Copyright (C) 2018 Marek.Gagolewski.com
All rights reserved.

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