sklearn.semi_supervised.LabelSpreading

class sklearn.semi_supervised.LabelSpreading(kernel='rbf', gamma=20, n_neighbors=7, alpha=0.2, max_iter=30, tol=0.001)

LabelSpreading model for semi-supervised learning

This model is similar to the basic Label Propgation algorithm, but uses affinity matrix based on the normalized graph Laplacian and soft clamping across the labels.

Parameters:

kernel : {‘knn’, ‘rbf’}

String identifier for kernel function to use. Only ‘rbf’ and ‘knn’ kernels are currently supported.

gamma : float

parameter for rbf kernel

n_neighbors : integer > 0

parameter for knn kernel

alpha : float

clamping factor

max_iter : float

maximum number of iterations allowed

tol : float

Convergence tolerance: threshold to consider the system at steady state

Attributes:

X_ : array, shape = [n_samples, n_features]

Input array.

classes_ : array, shape = [n_classes]

The distinct labels used in classifying instances.

label_distributions_ : array, shape = [n_samples, n_classes]

Categorical distribution for each item.

transduction_ : array, shape = [n_samples]

Label assigned to each item via the transduction.

n_iter_ : int

Number of iterations run.

See also

LabelPropagation

Unregularized graph based semi-supervised learning

References

Dengyong Zhou, Olivier Bousquet, Thomas Navin Lal, Jason Weston, Bernhard Schoelkopf. Learning with local and global consistency (2004) http://citeseer.ist.psu.edu/viewdoc/summary?doi=10.1.1.115.3219

Examples

>>> from sklearn import datasets
>>> from sklearn.semi_supervised import LabelSpreading
>>> label_prop_model = LabelSpreading()
>>> iris = datasets.load_iris()
>>> random_unlabeled_points = np.where(np.random.random_integers(0, 1,
...    size=len(iris.target)))
>>> labels = np.copy(iris.target)
>>> labels[random_unlabeled_points] = -1
>>> label_prop_model.fit(iris.data, labels)
... 
LabelSpreading(...)

Methods

fit(X, y)	Fit a semi-supervised label propagation model based
get_params([deep])	Get parameters for this estimator.
predict(X)	Performs inductive inference across the model.
predict_proba(X)	Predict probability for each possible outcome.
score(X, y[, sample_weight])	Returns the mean accuracy on the given test data and labels.
set_params(**params)	Set the parameters of this estimator.

__init__(kernel='rbf', gamma=20, n_neighbors=7, alpha=0.2, max_iter=30, tol=0.001)

fit(X, y)

Fit a semi-supervised label propagation model based

All the input data is provided matrix X (labeled and unlabeled) and corresponding label matrix y with a dedicated marker value for unlabeled samples.

Parameters:

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

A {n_samples by n_samples} size matrix will be created from this

y : array_like, shape = [n_samples]

n_labeled_samples (unlabeled points are marked as -1) All unlabeled samples will be transductively assigned labels

Returns:

self : returns an instance of self.

get_params(deep=True)

Get parameters for this estimator.

Parameters:

deep: boolean, optional :

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

Returns:

params : mapping of string to any

Parameter names mapped to their values.

predict(X)

Performs inductive inference across the model.

Parameters:

X : array_like, shape = [n_samples, n_features]

Returns:

y : array_like, shape = [n_samples]

Predictions for input data

predict_proba(X)

Predict probability for each possible outcome.

Compute the probability estimates for each single sample in X and each possible outcome seen during training (categorical distribution).

Parameters:

X : array_like, shape = [n_samples, n_features]

Returns:

probabilities : array, shape = [n_samples, n_classes]

Normalized probability distributions across class labels

score(X, y, sample_weight=None)

Returns the mean accuracy on the given test data and labels.

In multi-label classification, this is the subset accuracy which is a harsh metric since you require for each sample that each label set be correctly predicted.

Parameters:

X : array-like, shape = (n_samples, n_features)

Test samples.

y : array-like, shape = (n_samples) or (n_samples, n_outputs)

True labels for X.

sample_weight : array-like, shape = [n_samples], optional

Sample weights.

Returns:

score : float

Mean accuracy of self.predict(X) wrt. y.

set_params(**params)

Set the parameters of this 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 :

Examples using sklearn.semi_supervised.LabelSpreading

Label Propagation learning a complex structure

Decision boundary of label propagation versus SVM on the Iris dataset

Label Propagation digits: Demonstrating performance

Label Propagation digits active learning