8.17.17. sklearn.linear_model.PassiveAggressiveClassifier

class sklearn.linear_model.PassiveAggressiveClassifier(C=1.0, fit_intercept=True, n_iter=5, shuffle=False, verbose=0, loss='hinge', n_jobs=1, random_state=None, warm_start=False)

Passive Aggressive Classifier

Parameters:

C : float

Maximum step size (regularization). Defaults to 1.0.

fit_intercept: bool :

Whether the intercept should be estimated or not. If False, the data is assumed to be already centered. Defaults to True.

n_iter: int, optional :

The number of passes over the training data (aka epochs). Defaults to 5.

shuffle: bool, optional :

Whether or not the training data should be shuffled after each epoch. Defaults to False.

random_state: int seed, RandomState instance, or None (default) :

The seed of the pseudo random number generator to use when shuffling the data.

verbose: integer, optional :

The verbosity level

n_jobs: integer, optional :

The number of CPUs to use to do the OVA (One Versus All, for multi-class problems) computation. -1 means ‘all CPUs’. Defaults to 1.

loss : string, optional

The loss function to be used: hinge: equivalent to PA-I in the reference paper. squared_hinge: equivalent to PA-II in the reference paper.

warm_start : bool, optional

When set to True, reuse the solution of the previous call to fit as initialization, otherwise, just erase the previous solution.

See also

SGDClassifier, Perceptron

References

Online Passive-Aggressive Algorithms <http://jmlr.csail.mit.edu/papers/volume7/crammer06a/crammer06a.pdf> K. Crammer, O. Dekel, J. Keshat, S. Shalev-Shwartz, Y. Singer - JMLR (2006)

Attributes

coef_	array, shape = [1, n_features] if n_classes == 2 else [n_classes,
n_features]		Weights assigned to the features.
intercept_	array, shape = [1] if n_classes == 2 else [n_classes]	Constants in decision function.

Methods

decision_function(X)	Predict confidence scores for samples.
fit(X, y[, coef_init, intercept_init])	Fit linear model with Passive Aggressive algorithm.
get_params([deep])	Get parameters for the estimator
partial_fit(X, y[, classes])	Fit linear model with Passive Aggressive algorithm.
predict(X)	Predict class labels for samples in X.
score(X, y)	Returns the mean accuracy on the given test data and labels.
set_params(*args, **kwargs)

__init__(C=1.0, fit_intercept=True, n_iter=5, shuffle=False, verbose=0, loss='hinge', n_jobs=1, random_state=None, warm_start=False)

decision_function(X)

Predict confidence scores for samples.

The confidence score for a sample is the signed distance of that sample to the hyperplane.

Parameters:

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

Samples.

Returns:

array, shape = [n_samples] if n_classes == 2 else [n_samples,n_classes] :

Confidence scores per (sample, class) combination. In the binary case, confidence score for the “positive” class.

fit(X, y, coef_init=None, intercept_init=None)

Fit linear model with Passive Aggressive algorithm.

Parameters:

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

Training data

y : numpy array of shape [n_samples]

Target values

coef_init : array, shape = [n_classes,n_features]

The initial coeffients to warm-start the optimization.

intercept_init : array, shape = [n_classes]

The initial intercept to warm-start the optimization.

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

Weights applied to individual samples. If not provided, uniform weights are assumed.

Returns:

self : returns an instance of self.

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, classes=None)

Fit linear model with Passive Aggressive algorithm.

Parameters:

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

Subset of the training data

y : numpy array of shape [n_samples]

Subset of the target values

classes : array, shape = [n_classes]

Classes across all calls to partial_fit. Can be obtained by via np.unique(y_all), where y_all is the target vector of the entire dataset. This argument is required for the first call to partial_fit and can be omitted in the subsequent calls. Note that y doesn’t need to contain all labels in classes.

Returns:

self : returns an instance of self.

predict(X)

Predict class labels for samples in X.

Parameters:

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

Samples.

Returns:

C : array, shape = [n_samples]

Predicted class label per sample.

score(X, y)

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

Parameters:

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

Training set.

y : array-like, shape = [n_samples]

Labels for X.

Returns:

z : float

seed

DEPRECATED: Parameter ‘seed’ war renamed to ‘random_state’ for consistency and will be removed in 0.15