NearestCentroid.cpp

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/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * Written (W) 2012 Philippe Tillet
 */

#include <shogun/classifier/NearestCentroid.h>
#include <shogun/labels/MulticlassLabels.h>
#include <shogun/features/Features.h>
#include <shogun/features/FeatureTypes.h>



namespace shogun{
    
    CNearestCentroid::CNearestCentroid() : CDistanceMachine()
    {
        init();
    }

    CNearestCentroid::CNearestCentroid(CDistance* d, CLabels* trainlab) : CDistanceMachine()
    {
        init();
        ASSERT(d)
        ASSERT(trainlab)
        set_distance(d);
        set_labels(trainlab);
    }

    CNearestCentroid::~CNearestCentroid()
    {
        if(m_is_trained)
            distance->remove_lhs();
        else
            delete m_centroids;
    }

    void CNearestCentroid::init()
    {
        m_shrinking=0;
        m_is_trained=false;
        m_centroids = new CDenseFeatures<float64_t>();
    }


    bool CNearestCentroid::train_machine(CFeatures* data)
    {
        ASSERT(m_labels)
        ASSERT(m_labels->get_label_type() == LT_MULTICLASS)
        ASSERT(distance)
        ASSERT( data->get_feature_class() == C_DENSE)
        if (data)
        {
            if (m_labels->get_num_labels() != data->get_num_vectors())
                SG_ERROR("Number of training vectors does not match number of labels\n")
            distance->init(data, data);
        }
        else
        {
            data = distance->get_lhs();
        }
        int32_t num_vectors = data->get_num_vectors();
        int32_t num_classes = ((CMulticlassLabels*) m_labels)->get_num_classes();
        int32_t num_feats = ((CDenseFeatures<float64_t>*) data)->get_num_features();
        SGMatrix<float64_t> centroids(num_feats,num_classes);
        centroids.zero();

        m_centroids->set_num_features(num_feats);
        m_centroids->set_num_vectors(num_classes);
        
        int64_t* num_per_class = new int64_t[num_classes];
        for (int32_t i=0 ; i<num_classes ; i++)
        {
            num_per_class[i]=0;
        }
        
        for (int32_t idx=0 ; idx<num_vectors ; idx++)
        {
            int32_t current_len;
            bool current_free;
            int32_t current_class = ((CMulticlassLabels*) m_labels)->get_label(idx);
            float64_t* target = centroids.matrix + num_feats*current_class;
            float64_t* current = ((CDenseFeatures<float64_t>*)data)->get_feature_vector(idx,current_len,current_free);
            SGVector<float64_t>::add(target,1.0,target,1.0,current,current_len);
            num_per_class[current_class]++;
            ((CDenseFeatures<float64_t>*)data)->free_feature_vector(current, current_len, current_free);
        }


        for (int32_t i=0 ; i<num_classes ; i++)
        {
            float64_t* target = centroids.matrix + num_feats*i;
            int32_t total = num_per_class[i];
            float64_t scale = 0;
            if(total>1)
                scale = 1.0/((float64_t)(total-1));
            else
                scale = 1.0/(float64_t)total;
                
            SGVector<float64_t>::scale_vector(scale,target,num_feats);
        }
                
        m_centroids->free_feature_matrix();
        m_centroids->set_feature_matrix(centroids);
        
        
        m_is_trained=true;
        distance->init(m_centroids,distance->get_rhs());
        
        SG_FREE(num_per_class);
        
        return true;
    }

}