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请仔细看看这个程序是否会在netbeans中没有任何错误的情况下运行。这个程序的输出是什么？试图运行这个程序但是我得到的输出只读取了数据我给定的输入文件.arff file.im得到这样的输出：读0数据 最后行读：@attribute残疾人-婴儿{字符串，N，Y} 期待2个属性id3决策树程序
import java.io.*;
import java.util.*;
public class ID3
{
int numAttributes;
String []attributeNames;
Vector []domains;
/* The class to represent a data point consisting of numAttributes values
of attributes */
class DataPoint {
public int []attributes;
public DataPoint(int numattributes) {
attributes = new int[numattributes];
}
};
/* The class to represent a node in the decomposition tree.
*/
class TreeNode {
public double entropy;
public Vector data;
public int decompositionAttribute;
public int decompositionValue;
public TreeNode []children;
public TreeNode parent;
public TreeNode() {
data = new Vector();
}
};
TreeNode root = new TreeNode();
public int getSymbolValue(int attribute, String symbol) {
int index = domains[attribute].indexOf(symbol);
if (index < 0) {
domains[attribute].addElement(symbol);
return domains[attribute].size() -1;
}
return index;
}
public int []getAllValues(Vector data, int attribute) {
Vector values = new Vector();
int num = data.size();
for (int i=0; i< num; i++) {
DataPoint point = (DataPoint)data.elementAt(i);
String symbol =
(String)domains[attribute].elementAt(point.attributes[attribute]);
int index = values.indexOf(symbol);
if (index < 0) {
values.addElement(symbol);
}
}
int []array = new int[values.size()];
for (int i=0; i< array.length; i++) {
String symbol = (String)values.elementAt(i);
array[i] = domains[attribute].indexOf(symbol);
}
values = null;
return array;
}
public Vector getSubset(Vector data, int attribute, int value) {
Vector subset = new Vector();
int num = data.size();
for (int i=0; i< num; i++) {
DataPoint point = (DataPoint)data.elementAt(i);
if (point.attributes[attribute] == value) subset.addElement(point);
}
return subset;
}
public double calculateEntropy(Vector data) {
int numdata = data.size();
if (numdata == 0) return 0;
int attribute = numAttributes-1;
int numvalues = domains[attribute].size();
double sum = 0;
for (int i=0; i< numvalues; i++) {
int count=0;
for (int j=0; j< numdata; j++) {
DataPoint point = (DataPoint)data.elementAt(j);
if (point.attributes[attribute] == i) count++;
}
double probability = 1.*count/numdata;
if (count > 0) sum += -probability*Math.log(probability);
}
return sum;
}
public boolean alreadyUsedToDecompose(TreeNode node, int attribute) {
if (node.children != null) {
if (node.decompositionAttribute == attribute)
return true;
}
if (node.parent == null) return false;
return alreadyUsedToDecompose(node.parent, attribute);
}
public void decomposeNode(TreeNode node) {
double bestEntropy=0;
boolean selected=false;
int selectedAttribute=0;
int numdata = node.data.size();
int numinputattributes = numAttributes-1;
node.entropy = calculateEntropy(node.data);
if (node.entropy == 0) return;
for (int i=0; i< numinputattributes; i++) {
int numvalues = domains[i].size();
if (alreadyUsedToDecompose(node, i)) continue;
double averageentropy = 0;
for (int j=0; j< numvalues; j++) {
Vector subset = getSubset(node.data, i, j);
if (subset.size() == 0) continue;
double subentropy = calculateEntropy(subset);
averageentropy += subentropy *
subset.size();
}
averageentropy = averageentropy/numdata; //
Taking the weighted average
if (selected == false) {
selected = true;
bestEntropy = averageentropy;
selectedAttribute = i;
} else {
if (averageentropy < bestEntropy) {
selected = true;
bestEntropy = averageentropy;
selectedAttribute = i;
}
}
}
if (selected == false) return;
int numvalues = domains[selectedAttribute].size();
node.decompositionAttribute = selectedAttribute;
node.children = new TreeNode [numvalues];
for (int j=0; j< numvalues; j++) {
node.children[j] = new TreeNode();
node.children[j].parent = node;
node.children[j].data = getSubset(node.data,
selectedAttribute, j);
node.children[j].decompositionValue = j;
}
for (int j=0; j< numvalues; j++) {
decomposeNode(node.children[j]);
}
node.data = null;
}
public int readData(String filename) throws Exception {
FileInputStream in = null;
try {
File inputFile = new File(filename);
in = new FileInputStream(inputFile);
} catch (Exception e) {
System.err.println("Unable to open data file: " + filename + "n" + e);
return 0;
}
BufferedReader bin = new BufferedReader(new InputStreamReader(in));
String input;
while(true) {
input = bin.readLine();
if (input == null) {
System.err.println("No data found in the data file: " + filename +
"n");
return 0;
}
if (input.startsWith("//")) continue;
if (input.equals("")) continue;
break;
}
StringTokenizer tokenizer = new StringTokenizer(input);
numAttributes = tokenizer.countTokens();
if (numAttributes <= 1) {
System.err.println("Read line: " + input);
System.err.println("Could not obtain the names of attributes in the
line");
System.err.println("Expecting at least one input attribute and one
output attribute");
return 0;
}
domains = new Vector[numAttributes];
for (int i=0; i < numAttributes; i++) domains[i] = new Vector();
attributeNames = new String[numAttributes];
for (int i=0; i < numAttributes; i++) {
attributeNames[i] = tokenizer.nextToken();
}
while(true) {
input = bin.readLine();
if (input == null) break;
if (input.startsWith("//")) continue;
if (input.equals("")) continue;
tokenizer = new StringTokenizer(input);
int numtokens = tokenizer.countTokens();
if (numtokens != numAttributes) {
System.err.println("Read " + root.data.size() + " data");
System.err.println("Last line read: " + input);
System.err.println("Expecting " + numAttributes + " attributes");
return 0;
}
DataPoint point = new DataPoint(numAttributes);
for (int i=0; i < numAttributes; i++) {
point.attributes[i] = getSymbolValue(i, tokenizer.nextToken()
);
}
root.data.addElement(point);
}
bin.close();
return 1;
}
public void printTree(TreeNode node, String tab) {
int outputattr = numAttributes-1;
if (node.children == null) {
int []values = getAllValues(node.data, outputattr);
if (values.length == 1) {
System.out.println(tab + "t" + attributeNames[outputattr] + " = "" +
domains[outputattr].elementAt(values[0]) + "";");
return;
}
System.out.print(tab + "t" + attributeNames[outputattr] + " = {");
for (int i=0; i < values.length; i++) {
System.out.print(""" + domains[outputattr].elementAt(values[i]) + ""
");
if (i != values.length-1) System.out.print(" , ");
}
System.out.println(" };");
return;
}
int numvalues = node.children.length;
for (int i=0; i < numvalues; i++) {
System.out.println(tab + "if(" +
attributeNames[node.decompositionAttribute] + " == "" +
domains[node.decompositionAttribute].elementAt(i)
+ "") {");
printTree(node.children[i], tab + "t");
if (i != numvalues-1) System.out.print(tab + "} else ");
else System.out.println(tab + "}");
}
}
public void createDecisionTree() {
decomposeNode(root);
printTree(root, "");
}
/* main function */
public static void main(String[] args) throws Exception {
ID3 me = new ID3();
int status = me.readData("c:\\in.txt");
if (status <= 0) return;
me.createDecisionTree();
}
}