sklearn.cluster
.k_means¶
- sklearn.cluster.k_means(X, n_clusters, *, sample_weight=None, init='k-means++', n_init='auto', max_iter=300, verbose=False, tol=0.0001, random_state=None, copy_x=True, algorithm='lloyd', return_n_iter=False)[source]¶
Perform 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
. IfNone
, all observations are assigned equal weight.sample_weight
is not used during initialization ifinit
is a callable or a user provided array.- init{‘k-means++’, ‘random’}, callable or array-like of shape (n_clusters, n_features), 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'
: choosen_clusters
observations (rows) at random from data for the initial centroids.If an array 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.
- n_init‘auto’ or int, default=”auto”
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.
When
n_init='auto'
, the number of runs depends on the value of init: 10 if usinginit='random'
orinit
is a callable; 1 if usinginit='k-means++'
orinit
is an array-like.New in version 1.2: Added ‘auto’ option for
n_init
.Changed in version 1.4: Default value for
n_init
changed to'auto'
.- 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 or None, 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 ifcopy_x
is False. If the original data is sparse, but not in CSR format, a copy will be made even ifcopy_x
is False.- algorithm{“lloyd”, “elkan”}, default=”lloyd”
K-means algorithm to use. The classical EM-style algorithm is
"lloyd"
. The"elkan"
variation can be more efficient on some datasets 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)
.Changed in version 0.18: Added Elkan algorithm
Changed in version 1.1: Renamed “full” to “lloyd”, and deprecated “auto” and “full”. Changed “auto” to use “lloyd” instead of “elkan”.
- 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,)
The
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.
Examples
>>> import numpy as np >>> from sklearn.cluster import k_means >>> X = np.array([[1, 2], [1, 4], [1, 0], ... [10, 2], [10, 4], [10, 0]]) >>> centroid, label, inertia = k_means( ... X, n_clusters=2, n_init="auto", random_state=0 ... ) >>> centroid array([[10., 2.], [ 1., 2.]]) >>> label array([1, 1, 1, 0, 0, 0], dtype=int32) >>> inertia 16.0