- 代码: 全选
/*
* 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 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
* EntropyBasedSplitCrit.java
* Copyright (C) 1999 University of Waikato, Hamilton, New Zealand
*
*/
package weka.classifiers.trees.j48;
/**
* "Abstract" class for computing splitting criteria
* based on the entropy of a class distribution.
*
* @author Eibe Frank (eibe@cs.waikato.ac.nz)
* @version $Revision: 1.8 $
*/
public abstract class EntropyBasedSplitCrit
extends SplitCriterion {
/** for serialization */
private static final long serialVersionUID = -2618691439791653056L;
/** The log of 2. */
protected static double log2 = Math.log(2);
/**
* Help method for computing entropy.
*/
public final double logFunc(double num) {
// Constant hard coded for efficiency reasons
if (num < 1e-6)
return 0;
else
return num*Math.log(num)/log2;
//此处的num是什么参数啊
}
/**
* Computes entropy of distribution before splitting.
*/
public final double oldEnt(Distribution bags) {
double returnValue = 0;
int j;
for (j=0;j<bags.numClasses();j++)
returnValue = returnValue+logFunc(bags.perClass(j));
return logFunc(bags.total())-returnValue;
//这里它返回的参数logFunc(bags.total())-returnValue;又是什么啊
}
/**
* Computes entropy of distribution after splitting.
*/
public final double newEnt(Distribution bags) {
double returnValue = 0;
int i,j;
for (i=0;i<bags.numBags();i++){
for (j=0;j<bags.numClasses();j++)
returnValue = returnValue+logFunc(bags.perClassPerBag(i,j));
returnValue = returnValue-logFunc(bags.perBag(i));
}
return -returnValue;
//还有这里 }
/**
* Computes entropy after splitting without considering the
* class values.
*/
public final double splitEnt(Distribution bags) {
double returnValue = 0;
int i;
for (i=0;i<bags.numBags();i++)
returnValue = returnValue+logFunc(bags.perBag(i));
return logFunc(bags.total())-returnValue;
}
}
怎么与原始公式中的参数对应不上呢？
这个与公式中
的也对不上啊。。。