Compute the mean Silhouette Coefficient of all samples.
The Silhouette Coefficient is calculated using the mean intra-cluster distance (a
) and the mean nearest-cluster distance (b
) for each sample. The Silhouette Coefficient for a sample is (b - a) / max(a, b)
. To clarify, b
is the distance between a sample and the nearest cluster that the sample is not a part of. Note that Silhouette Coefficient is only defined if number of labels is 2 <= n_labels <= n_samples - 1
.
This function returns the mean Silhouette Coefficient over all samples. To obtain the values for each sample, use silhouette_samples
.
The best value is 1 and the worst value is -1. Values near 0 indicate overlapping clusters. Negative values generally indicate that a sample has been assigned to the wrong cluster, as a different cluster is more similar.
Read more in the User Guide.
An array of pairwise distances between samples, or a feature array.
Predicted labels for each sample.
The metric to use when calculating distance between instances in a feature array. If metric is a string, it must be one of the options allowed by pairwise_distances
. If X
is the distance array itself, use metric="precomputed"
.
The size of the sample to use when computing the Silhouette Coefficient on a random subset of the data. If sample_size is None
, no sampling is used.
Determines random number generation for selecting a subset of samples. Used when sample_size is not None
. Pass an int for reproducible results across multiple function calls. See Glossary.
Any further parameters are passed directly to the distance function. If using a scipy.spatial.distance metric, the parameters are still metric dependent. See the scipy docs for usage examples.
Mean Silhouette Coefficient for all samples.
References
Examples
>>> from sklearn.datasets import make_blobs >>> from sklearn.cluster import KMeans >>> from sklearn.metrics import silhouette_score >>> X, y = make_blobs(random_state=42) >>> kmeans = KMeans(n_clusters=2, random_state=42) >>> silhouette_score(X, kmeans.fit_predict(X)) 0.49...
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