sklearn.cluster.k_means¶

sklearn.cluster.k_means(X, n_clusters, *, sample_weight=None, init='k-means++', precompute_distances='deprecated', n_init=10, max_iter=300, verbose=False, tol=0.0001, random_state=None, copy_x=True, n_jobs='deprecated', algorithm='auto', return_n_iter=False)[source]¶

K-means clustering algorithm.

Read more in the User Guide.

Parameters

X{array-like, sparse} matrix of shape (n_samples, n_features)

The observations to cluster. It must be noted that the data will be converted to C ordering, which will cause a memory copy if the given data is not C-contiguous.

n_clustersint

The number of clusters to form as well as the number of centroids to generate.

sample_weightarray-like of shape (n_samples,), default=None

The weights for each observation in X. If None, all observations are assigned equal weight

init{‘k-means++’, ‘random’, ndarray, callable}, default=’k-means++’

Method for initialization:

‘k-means++’ : selects initial cluster centers for k-mean clustering in a smart way to speed up convergence. See section Notes in k_init for more details.

‘random’: choose n_clusters observations (rows) at random from data for the initial centroids.

If an ndarray is passed, it should be of shape (n_clusters, n_features) and gives the initial centers.

If a callable is passed, it should take arguments X, n_clusters and a random state and return an initialization.

precompute_distances{‘auto’, True, False}

Precompute distances (faster but takes more memory).

‘auto’ : do not precompute distances if n_samples * n_clusters > 12 million. This corresponds to about 100MB overhead per job using double precision.

True : always precompute distances

False : never precompute distances

Deprecated since version 0.23: ‘precompute_distances’ was deprecated in version 0.23 and will be removed in 0.25. It has no effect.

n_initint, default=10

Number of time the k-means algorithm will be run with different centroid seeds. The final results will be the best output of n_init consecutive runs in terms of inertia.

max_iterint, default=300

Maximum number of iterations of the k-means algorithm to run.

verbosebool, default=False

Verbosity mode.

tolfloat, default=1e-4

Relative tolerance with regards to Frobenius norm of the difference in the cluster centers of two consecutive iterations to declare convergence.

random_stateint, RandomState instance, default=None

Determines random number generation for centroid initialization. Use an int to make the randomness deterministic. See Glossary.

copy_xbool, default=True

When pre-computing distances it is more numerically accurate to center the data first. If copy_x is True (default), then the original data is not modified. If False, the original data is modified, and put back before the function returns, but small numerical differences may be introduced by subtracting and then adding the data mean. Note that if the original data is not C-contiguous, a copy will be made even if copy_x is False. If the original data is sparse, but not in CSR format, a copy will be made even if copy_x is False.

n_jobsint, default=None

The number of OpenMP threads to use for the computation. Parallelism is sample-wise on the main cython loop which assigns each sample to its closest center.

None or -1 means using all processors.

Deprecated since version 0.23: n_jobs was deprecated in version 0.23 and will be removed in 0.25.

algorithm{“auto”, “full”, “elkan”}, default=”auto”

K-means algorithm to use. The classical EM-style algorithm is “full”. The “elkan” variation is more efficient on data with well-defined clusters, by using the triangle inequality. However it’s more memory intensive due to the allocation of an extra array of shape (n_samples, n_clusters).

For now “auto” (kept for backward compatibiliy) chooses “elkan” but it might change in the future for a better heuristic.

return_n_iterbool, default=False

Whether or not to return the number of iterations.

Returns

centroidndarray of shape (n_clusters, n_features)

Centroids found at the last iteration of k-means.

labelndarray of shape (n_samples,)

label[i] is the code or index of the centroid the i’th observation is closest to.

inertiafloat

The final value of the inertia criterion (sum of squared distances to the closest centroid for all observations in the training set).

best_n_iterint

Number of iterations corresponding to the best results. Returned only if return_n_iter is set to True.