/**
* This file is part of FNLP (formerly FudanNLP).
*
* FNLP is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* FNLP is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with FudanNLP. If not, see <http://www.gnu.org/licenses/>.
*
* Copyright 2009-2014 www.fnlp.org. All rights reserved.
*/
package org.fnlp.nlp.pipe;
import java.io.Serializable;
import java.util.Iterator;
import org.fnlp.ml.types.Instance;
import org.fnlp.ml.types.sv.HashSparseVector;
import org.fnlp.ml.types.sv.SparseVector;
import gnu.trove.iterator.TIntFloatIterator;
/**
* 计算IFIDF
*
* @author xpqiu
*
*/
public class TFIDF extends Pipe implements Serializable {
private static final long serialVersionUID = 2937341538282834618L;
int[] idf;
private int docNum;
public TFIDF(int[] idf, int docNum) {
this.idf = idf;
this.docNum = docNum;
}
@Override
public void addThruPipe(Instance inst) {
HashSparseVector data = (HashSparseVector) inst.getData();
TIntFloatIterator it = data.data.iterator();
while (it.hasNext()) {
it.advance();
int id = it.key();
if (idf[id] > 0) {
float value = (float) (it.value()*Math.log(docNum / idf[id]));
data.put(id, value);
}
}
}
}