MLPACK  1.0.4
Public Member Functions | Private Attributes
mlpack::naive_bayes::NaiveBayesClassifier< MatType > Class Template Reference

The simple Naive Bayes classifier. More...

List of all members.

Public Member Functions

 NaiveBayesClassifier (const MatType &data, const size_t classes)
 Initializes the classifier as per the input and then trains it by calculating the sample mean and variances.
void Classify (const MatType &data, arma::Col< size_t > &results)
 Given a bunch of data points, this function evaluates the class of each of those data points, and puts it in the vector 'results'.
const MatType & Means () const
 Get the sample means for each class.
MatType & Means ()
 Modify the sample means for each class.
const arma::vec & Probabilities () const
 Get the prior probabilities for each class.
arma::vec & Probabilities ()
 Modify the prior probabilities for each class.
const MatType & Variances () const
 Get the sample variances for each class.
MatType & Variances ()
 Modify the sample variances for each class.

Private Attributes

MatType means
 Sample mean for each class.
arma::vec probabilities
 Class probabilities.
MatType variances
 Sample variances for each class.

Detailed Description

template<typename MatType = arma::mat>
class mlpack::naive_bayes::NaiveBayesClassifier< MatType >

The simple Naive Bayes classifier.

This class trains on the data by calculating the sample mean and variance of the features with respect to each of the labels, and also the class probabilities. The class labels are assumed to be positive integers (starting with 0), and are expected to be the last row of the data input to the constructor.

Mathematically, it computes P(X_i = x_i | Y = y_j) for each feature X_i for each of the labels y_j. Alongwith this, it also computes the classs probabilities P(Y = y_j).

For classifying a data point (x_1, x_2, ..., x_n), it computes the following: arg max_y(P(Y = y)*P(X_1 = x_1 | Y = y) * ... * P(X_n = x_n | Y = y))

Example use:

 extern arma::mat training_data, testing_data;
 NaiveBayesClassifier<> nbc(training_data, 5);
 arma::vec results;

 nbc.Classify(testing_data, results);

Definition at line 58 of file naive_bayes_classifier.hpp.


Constructor & Destructor Documentation

template<typename MatType = arma::mat>
mlpack::naive_bayes::NaiveBayesClassifier< MatType >::NaiveBayesClassifier ( const MatType &  data,
const size_t  classes 
)

Initializes the classifier as per the input and then trains it by calculating the sample mean and variances.

The input data is expected to have integer labels as the last row (starting with 0 and not greater than the number of classes).

Example use:

 extern arma::mat training_data, testing_data;
 NaiveBayesClassifier nbc(training_data, 5);
Parameters:
dataSample data points; the last row should be labels.
classesNumber of classes in this classifier.

Member Function Documentation

template<typename MatType = arma::mat>
void mlpack::naive_bayes::NaiveBayesClassifier< MatType >::Classify ( const MatType &  data,
arma::Col< size_t > &  results 
)

Given a bunch of data points, this function evaluates the class of each of those data points, and puts it in the vector 'results'.

 arma::mat test_data; // each column is a test point
 arma::Col<size_t> results;
 ...
 nbc.Classify(test_data, &results);
Parameters:
dataList of data points.
resultsVector that class predictions will be placed into.
template<typename MatType = arma::mat>
const MatType& mlpack::naive_bayes::NaiveBayesClassifier< MatType >::Means ( ) const [inline]

Get the sample means for each class.

Definition at line 105 of file naive_bayes_classifier.hpp.

References mlpack::naive_bayes::NaiveBayesClassifier< MatType >::means.

template<typename MatType = arma::mat>
MatType& mlpack::naive_bayes::NaiveBayesClassifier< MatType >::Means ( ) [inline]

Modify the sample means for each class.

Definition at line 107 of file naive_bayes_classifier.hpp.

References mlpack::naive_bayes::NaiveBayesClassifier< MatType >::means.

template<typename MatType = arma::mat>
const arma::vec& mlpack::naive_bayes::NaiveBayesClassifier< MatType >::Probabilities ( ) const [inline]

Get the prior probabilities for each class.

Definition at line 115 of file naive_bayes_classifier.hpp.

References mlpack::naive_bayes::NaiveBayesClassifier< MatType >::probabilities.

template<typename MatType = arma::mat>
arma::vec& mlpack::naive_bayes::NaiveBayesClassifier< MatType >::Probabilities ( ) [inline]

Modify the prior probabilities for each class.

Definition at line 117 of file naive_bayes_classifier.hpp.

References mlpack::naive_bayes::NaiveBayesClassifier< MatType >::probabilities.

template<typename MatType = arma::mat>
const MatType& mlpack::naive_bayes::NaiveBayesClassifier< MatType >::Variances ( ) const [inline]

Get the sample variances for each class.

Definition at line 110 of file naive_bayes_classifier.hpp.

References mlpack::naive_bayes::NaiveBayesClassifier< MatType >::variances.

template<typename MatType = arma::mat>
MatType& mlpack::naive_bayes::NaiveBayesClassifier< MatType >::Variances ( ) [inline]

Modify the sample variances for each class.

Definition at line 112 of file naive_bayes_classifier.hpp.

References mlpack::naive_bayes::NaiveBayesClassifier< MatType >::variances.


Member Data Documentation

template<typename MatType = arma::mat>
MatType mlpack::naive_bayes::NaiveBayesClassifier< MatType >::means [private]

Sample mean for each class.

Definition at line 62 of file naive_bayes_classifier.hpp.

Referenced by mlpack::naive_bayes::NaiveBayesClassifier< MatType >::Means().

template<typename MatType = arma::mat>
arma::vec mlpack::naive_bayes::NaiveBayesClassifier< MatType >::probabilities [private]

Class probabilities.

Definition at line 68 of file naive_bayes_classifier.hpp.

Referenced by mlpack::naive_bayes::NaiveBayesClassifier< MatType >::Probabilities().

template<typename MatType = arma::mat>
MatType mlpack::naive_bayes::NaiveBayesClassifier< MatType >::variances [private]

Sample variances for each class.

Definition at line 65 of file naive_bayes_classifier.hpp.

Referenced by mlpack::naive_bayes::NaiveBayesClassifier< MatType >::Variances().


The documentation for this class was generated from the following file: