sklearn.cluster.dbscan

sklearn.cluster.dbscan(X, eps=0.5, min_samples=5, metric=’minkowski’, metric_params=None, algorithm=’auto’, leaf_size=30, p=2, sample_weight=None, n_jobs=1)

Perform DBSCAN clustering from vector array or distance matrix.

Read more in the User Guide.

Parameters:

X : array or sparse (CSR) matrix of shape (n_samples, n_features), or array of shape (n_samples, n_samples)

A feature array, or array of distances between samples if metric='precomputed'.

eps : float, optional

The maximum distance between two samples for them to be considered as in the same neighborhood.

min_samples : int, optional

The number of samples (or total weight) in a neighborhood for a point to be considered as a core point. This includes the point itself.

metric : string, or callable

The metric to use when calculating distance between instances in a feature array. If metric is a string or callable, it must be one of the options allowed by metrics.pairwise.pairwise_distances for its metric parameter. If metric is “precomputed”, X is assumed to be a distance matrix and must be square. X may be a sparse matrix, in which case only “nonzero” elements may be considered neighbors for DBSCAN.

metric_params : dict, optional

Additional keyword arguments for the metric function.

New in version 0.19.

algorithm : {‘auto’, ‘ball_tree’, ‘kd_tree’, ‘brute’}, optional

The algorithm to be used by the NearestNeighbors module to compute pointwise distances and find nearest neighbors. See NearestNeighbors module documentation for details.

leaf_size : int, optional (default = 30)

Leaf size passed to BallTree or cKDTree. This can affect the speed of the construction and query, as well as the memory required to store the tree. The optimal value depends on the nature of the problem.

p : float, optional

The power of the Minkowski metric to be used to calculate distance between points.

sample_weight : array, shape (n_samples,), optional

Weight of each sample, such that a sample with a weight of at least min_samples is by itself a core sample; a sample with negative weight may inhibit its eps-neighbor from being core. Note that weights are absolute, and default to 1.

n_jobs : int, optional (default = 1)

The number of parallel jobs to run for neighbors search. If -1, then the number of jobs is set to the number of CPU cores.

Returns:

core_samples : array [n_core_samples]

Indices of core samples.

labels : array [n_samples]

Cluster labels for each point. Noisy samples are given the label -1.

Notes

For an example, see examples/cluster/plot_dbscan.py.

This implementation bulk-computes all neighborhood queries, which increases the memory complexity to O(n.d) where d is the average number of neighbors, while original DBSCAN had memory complexity O(n).

Sparse neighborhoods can be precomputed using NearestNeighbors.radius_neighbors_graph with mode='distance'.

References

Ester, M., H. P. Kriegel, J. Sander, and X. Xu, “A Density-Based Algorithm for Discovering Clusters in Large Spatial Databases with Noise”. In: Proceedings of the 2nd International Conference on Knowledge Discovery and Data Mining, Portland, OR, AAAI Press, pp. 226-231. 1996