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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
/**
* @author Peter Boros
* @date 2004/08/20
* @version $Id$
* @file vectorizer.cpp
* @brief Simple document vectorizer based on %FSA (%Finite %State %Automaton) (implementation)
*/
#include <list>
#include <algorithm>
#include <cmath>
#include "vectorizer.h"
#include "fsa.h"
namespace fsa {
// {{{ Vectorizer::TfIdf::weight
double Vectorizer::TfIdf::weight(unsigned int tfnorm, unsigned int idfnorm,
double tfexp, double idfexp) const
{
double tf_n, idf_n;
if(tfnorm==0 || tfexp==0.0){
tf_n = 1.0;
}
else{
tf_n = (double)_tf/tfnorm;
if(tfexp!=1.0 && tf_n!=0.0){
tf_n = std::exp(tfexp * std::log(tf_n));
}
}
if(idfnorm==0 || idfexp==0.0){
idf_n = 1.0;
}
else{
idf_n = 1.0-(double)_idf/idfnorm;
if(idf_n<0.0)
idf_n = 0.0;
if(idfexp!=1.0 && idf_n!=0.0){
idf_n = std::exp(idfexp * std::log(idf_n));
}
}
return tf_n * idf_n;
}
// }}}
// {{{ Vectorizer::vectorize
void Vectorizer::vectorize(const NGram &text, TermVector &vector, unsigned int limit,
bool keephits, double tfexp, double idfexp) const
{
RawVector raw_vect(keephits);
RawVector::iterator rvi;
_detector.detect(text,raw_vect);
vector.clear();
unsigned int tfmax=1;
for(rvi=raw_vect.begin(); rvi!=raw_vect.end(); ++rvi){
if(rvi->second.first.tf()>tfmax)
tfmax=rvi->second.first.tf();
}
vector.reserve(raw_vect.size());
for(rvi=raw_vect.begin(); rvi!=raw_vect.end(); ++rvi){
vector.push_back(VectorItem(rvi->first,rvi->second.first.weight(tfmax,_idf_docs,tfexp,idfexp),rvi->second.second));
}
std::sort(vector.begin(),vector.end());
if(vector.size()>limit){
vector.resize(limit);
}
}
void Vectorizer::vectorize(const NGram &text, TermVector &vector, unsigned int limit,
double tfexp, double idfexp) const
{
vectorize(text, vector, limit, false, tfexp, idfexp);
}
// }}}
} // namespace fsa
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