8.1.1.4. sklearn.cluster.MiniBatchKMeans

class sklearn.cluster.MiniBatchKMeans(n_clusters=8, init='k-means++', max_iter=100, batch_size=100, verbose=0, compute_labels=True, random_state=None, tol=0.0, max_no_improvement=10, init_size=None, n_init=3, k=None, reassignment_ratio=0.01)

Mini-Batch K-Means clustering

Parameters:

n_clusters : int, optional, default: 8

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

max_iter : int, optional

Maximum number of iterations over the complete dataset before stopping independently of any early stopping criterion heuristics.

max_no_improvement : int, optional

Control early stopping based on the consecutive number of mini batches that does not yield an improvement on the smoothed inertia.

To disable convergence detection based on inertia, set max_no_improvement to None.

tol : float, optional

Control early stopping based on the relative center changes as measured by a smoothed, variance-normalized of the mean center squared position changes. This early stopping heuristics is closer to the one used for the batch variant of the algorithms but induces a slight computational and memory overhead over the inertia heuristic.

To disable convergence detection based on normalized center change, set tol to 0.0 (default).

batch_size: int, optional, default: 100 :

Size of the mini batches.

init_size: int, optional, default: 3 * batch_size :

Number of samples to randomly sample for speeding up the initialization (sometimes at the expense of accurracy): the only algorithm is initialized by running a batch KMeans on a random subset of the data. This needs to be larger than k.

init : {‘k-means++’, ‘random’ or an ndarray}

Method for initialization, defaults to ‘k-means++’:

‘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 k 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.

compute_labels: boolean :

Compute label assignements and inertia for the complete dataset once the minibatch optimization has converged in fit.

random_state: integer or numpy.RandomState, optional :

The generator used to initialize the centers. If an integer is given, it fixes the seed. Defaults to the global numpy random number generator.

reassignment_ratio: float, optional :

Control the fraction of the maximum number of counts for a center to be reassigned. A higher value means that low count centers are more easily reassigned, which means that the model will take longer to converge, but should converge in a better clustering.

Notes

See http://www.eecs.tufts.edu/~dsculley/papers/fastkmeans.pdf

Attributes

cluster_centers_: array, [n_clusters, n_features]	Coordinates of cluster centers
labels_:	Labels of each point (if compute_labels is set to True).
inertia_: float	The value of the inertia criterion associated with the chosen partition (if compute_labels is set to True). The inertia is defined as the sum of square distances of samples to their nearest neighbor.

Methods

fit(X[, y])	Compute the centroids on X by chunking it into mini-batches.
fit_predict(X)	Compute cluster centers and predict cluster index for each sample.
fit_transform(X[, y])	Compute clustering and transform X to cluster-distance space.
get_params([deep])	Get parameters for the estimator
partial_fit(X[, y])	Update k means estimate on a single mini-batch X.
predict(X)	Predict the closest cluster each sample in X belongs to.
score(X)	Opposite of the value of X on the K-means objective.
set_params(**params)	Set the parameters of the estimator.
transform(X[, y])	Transform X to a cluster-distance space

__init__(n_clusters=8, init='k-means++', max_iter=100, batch_size=100, verbose=0, compute_labels=True, random_state=None, tol=0.0, max_no_improvement=10, init_size=None, n_init=3, k=None, reassignment_ratio=0.01)

fit(X, y=None)

Compute the centroids on X by chunking it into mini-batches.

Parameters:

X: array-like, shape = [n_samples, n_features] :

Coordinates of the data points to cluster

fit_predict(X)

Compute cluster centers and predict cluster index for each sample.

Convenience method; equivalent to calling fit(X) followed by predict(X).

fit_transform(X, y=None)

Compute clustering and transform X to cluster-distance space.

Equivalent to fit(X).transform(X), but more efficiently implemented.

get_params(deep=True)

Get parameters for the estimator

Parameters:

deep: boolean, optional :

If True, will return the parameters for this estimator and contained subobjects that are estimators.

partial_fit(X, y=None)

Update k means estimate on a single mini-batch X.

Parameters:

X: array-like, shape = [n_samples, n_features] :

Coordinates of the data points to cluster.

predict(X)

Predict the closest cluster each sample in X belongs to.

In the vector quantization literature, cluster_centers_ is called the code book and each value returned by predict is the index of the closest code in the code book.

Parameters:

X: {array-like, sparse matrix}, shape = [n_samples, n_features] :

New data to predict.

Returns:

Y : array, shape [n_samples,]

Index of the closest center each sample belongs to.

score(X)

Opposite of the value of X on the K-means objective.

Parameters:

X: {array-like, sparse matrix}, shape = [n_samples, n_features] :

New data.

Returns:

score: float :

Opposite of the value of X on the K-means objective.

set_params(**params)

Set the parameters of the estimator.

The method works on simple estimators as well as on nested objects (such as pipelines). The former have parameters of the form <component>__<parameter> so that it’s possible to update each component of a nested object.

Returns:self :

transform(X, y=None)

Transform X to a cluster-distance space

In the new space, each dimension is the distance to the cluster centers. Note that even if X is sparse, the array returned by transform will typically be dense.

Parameters:

X: {array-like, sparse matrix}, shape = [n_samples, n_features] :

New data to transform.

Returns:

X_new : array, shape [n_samples, k]

X transformed in the new space.