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Naive Bayes classifier for multinomial models
The multinomial Naive Bayes classifier is suitable for classification with discrete features (e.g., word counts for text classification). The multinomial distribution normally requires integer feature counts. However, in practice, fractional counts such as tf-idf may also work.
Read more in the User Guide.
Parameters: | alpha : float, optional (default=1.0)
fit_prior : boolean
class_prior : array-like, size (n_classes,)
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Attributes: | class_log_prior_ : array, shape (n_classes, )
intercept_ : property
feature_log_prob_ : array, shape (n_classes, n_features)
coef_ : property
class_count_ : array, shape (n_classes,)
feature_count_ : array, shape (n_classes, n_features)
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Notes
For the rationale behind the names coef_ and intercept_, i.e. naive Bayes as a linear classifier, see J. Rennie et al. (2003), Tackling the poor assumptions of naive Bayes text classifiers, ICML.
References
C.D. Manning, P. Raghavan and H. Schuetze (2008). Introduction to Information Retrieval. Cambridge University Press, pp. 234-265. nlp.stanford.edu/IR-book/html/htmledition/naive-bayes-text-classification-1.html
Examples
>>> import numpy as np >>> X = np.random.randint(5, size=(6, 100)) >>> y = np.array([1, 2, 3, 4, 5, 6]) >>> from sklearn.naive_bayes import MultinomialNB >>> clf = MultinomialNB() >>> clf.fit(X, y) MultinomialNB(alpha=1.0, class_prior=None, fit_prior=True) >>> print(clf.predict(X[2:3])) [3]
Methods
fit(X, y[, sample_weight]) | Fit Naive Bayes classifier according to X, y |
get_params([deep]) | Get parameters for this estimator. |
partial_fit(X, y[, classes, sample_weight]) | Incremental fit on a batch of samples. |
predict(X) | Perform classification on an array of test vectors X. |
predict_log_proba(X) | Return log-probability estimates for the test vector X. |
predict_proba(X) | Return probability estimates for the test vector X. |
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. |
Fit Naive Bayes classifier according to X, y
Parameters: | X : {array-like, sparse matrix}, shape = [n_samples, n_features]
y : array-like, shape = [n_samples]
sample_weight : array-like, shape = [n_samples], optional
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Returns: | self : object
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Get parameters for this estimator.
Parameters: | deep: boolean, optional :
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Returns: | params : mapping of string to any
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Incremental fit on a batch of samples.
This method is expected to be called several times consecutively on different chunks of a dataset so as to implement out-of-core or online learning.
This is especially useful when the whole dataset is too big to fit in memory at once.
This method has some performance overhead hence it is better to call partial_fit on chunks of data that are as large as possible (as long as fitting in the memory budget) to hide the overhead.
Parameters: | X : {array-like, sparse matrix}, shape = [n_samples, n_features]
y : array-like, shape = [n_samples]
classes : array-like, shape = [n_classes]
sample_weight : array-like, shape = [n_samples], optional
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Returns: | self : object
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Perform classification on an array of test vectors X.
Parameters: | X : array-like, shape = [n_samples, n_features] |
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Returns: | C : array, shape = [n_samples]
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Return log-probability estimates for the test vector X.
Parameters: | X : array-like, shape = [n_samples, n_features] |
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Returns: | C : array-like, shape = [n_samples, n_classes]
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Return probability estimates for the test vector X.
Parameters: | X : array-like, shape = [n_samples, n_features] |
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Returns: | C : array-like, shape = [n_samples, n_classes]
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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)
y : array-like, shape = (n_samples) or (n_samples, n_outputs)
sample_weight : array-like, shape = [n_samples], optional
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Returns: | score : float
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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 : |
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Out-of-core classification of text documents
Classification of text documents: using a MLComp dataset
Classification of text documents using sparse features