Source code for Orange.classification.naive_bayes

import numpy as np

from Orange.classification import Learner, Model
from import Instance, Storage
from Orange.statistics import contingency
from Orange.preprocess import Discretize, RemoveNaNColumns

__all__ = ["NaiveBayesLearner"]

[docs]class NaiveBayesLearner(Learner): """ Naive Bayes classifier. Works only with discrete attributes. By default, continuous attributes are discretized. Parameters ---------- preprocessors : list, optional (default="[Orange.preprocess.Discretize]") An ordered list of preprocessors applied to data before training or testing. """ preprocessors = [RemoveNaNColumns(), Discretize()] name = 'naive bayes'
[docs] def fit_storage(self, table): if not isinstance(table, Storage): raise TypeError("Data is not a subclass of") if not all(var.is_discrete for var in table.domain.variables): raise NotImplementedError("Only discrete variables are supported.") cont = contingency.get_contingencies(table) class_freq = np.array(np.diag( contingency.get_contingency(table, table.domain.class_var))) class_prob = (class_freq + 1) / (np.sum(class_freq) + len(class_freq)) log_cont_prob = [np.log( (np.array(c) + 1) / (np.sum(np.array(c), axis=0)[None, :] + c.shape[0]) / class_prob[:, None]) for c in cont] return NaiveBayesModel(log_cont_prob, class_prob, table.domain)
class NaiveBayesModel(Model): def __init__(self, log_cont_prob, class_prob, domain): super().__init__(domain) self.log_cont_prob = log_cont_prob self.class_prob = class_prob def predict_storage(self, data): if isinstance(data, Instance): data = [data] if len(data.domain.attributes) == 0: probs = np.tile(self.class_prob, (len(data), 1)) else: isnan = np.isnan probs = np.exp( np.log(self.class_prob) + np.array([np.zeros_like(self.class_prob) if isnan(ins.x).all() else np.sum(attr_prob[:, int(attr_val)] for attr_val, attr_prob in zip(ins, self.log_cont_prob) if not isnan(attr_val)) for ins in data])) probs /= probs.sum(axis=1)[:, None] values = probs.argmax(axis=1) return values, probs NaiveBayesLearner.__returns__ = NaiveBayesModel