tfidf 做自然語言理解的經常用。文檔的作爲權重計算，
許多初學者搞不清楚，權重計算特徵選擇。
針對文本分類而言 作爲很簡單的說明，特徵選擇都跟 類別有關比如 卡方 信息增益
而權重計算則與類別無關 比如 tfidf，tf
具體公式請參看 http://zh.wikipedia.org/wiki/TF-IDF
下面代碼 寫的比較粗陋。高手請避開。，，，，，
訓練集可以上搜狗數據集上下載
寫完以後感覺還是matlab 比較爽啊。。幾行 解決java100多行的代碼
public class TfIdfcomputor {
static String path = "E:\\訓練集\\train\\";
static String vsmpath = "E:\\訓練集\\vsm\\vsm.txt";
//static String path = "E:\\訓練集\\SogouC.reduced\\Reduced";
// static String path ="E:\\訓練集\\SogouC.mini\\Sample";
static Map<String, Map<String, Double>> DFdic = new HashMap();
static HashMap<String, List<Map<String, Double>>> dic = new HashMap();
static int DCOUNT;
static HashMap<String, Double> idfDic = new HashMap();
static Map<String, Map<String,Double>> TFIDFdic = new HashMap();
// static Map<String,List<String>> Simpledic= new HashMap();
public static void main(String[] args) throws IOException {
TfIdfcomputor tf = new TfIdfcomputor();
File[] Filelist = tf.readData(path);
DCOUNT = Filelist.length;
tf.readir(Filelist);
System.out.println("DFdic");
tf.computeIDF(dic);
tf.ComputeTFIDF();
/* for( String s :TFIDFdic.keySet())
{
Map map = TFIDFdic.get(s);
for(Object key :map.keySet() )
{
System.out.println("file "+s +"word "+ key+" tfidf "+map.get(key));
}
}*/
System.out.println("計算完畢開始輸出");
tf.toLibData();
}
public void readir(File[] dir) throws IOException {
File[] fileList = dir;
for(File f :fileList){
System.out.println(f.getPath());
}
for (int i = 0; i < fileList.length; i++) {
File f = fileList[i];
//System.out.println(f.getPath());
String[] textword = cutWord(FiletoText(f.getPath()));
Map tf = computeTf(textword);
DFdic.put(f.getPath(), tf);
addDic(f.getPath(), tf);
}
System.out.println("TF PROCESS IS OVER");
System.out.println(dic.size());
for (Object o : dic.keySet()) {
System.out.println(o);
List list = dic.get(o);
for (Object l : list) {
Map pair = (Map) l;
for (Object p : pair.keySet()) {
/* System.out.println("key" + (String) o + "..."
+ "filepath...." + p + "tf..." + pair.get(p));*/
}
}
}
}
public String FiletoText(String path) throws IOException {
File f = new File(path);
BufferedReader br = new BufferedReader(new InputStreamReader(
new FileInputStream(f), "GB2312"));
String result = "";
String temp;
while ((temp = br.readLine()) != null) {
result = result + temp;
}
br.close();
return result;
}
public String[] cutWord(String text) throws IOException {
MMAnalyzer analyzer = new MMAnalyzer();
String temp = analyzer.segment(text, "|");
//System.out.println(temp);
String[] result = temp.split("\\|");
/*
* for(String s :result ) { System.out.println(s); }
*/
return result;
}
public HashMap<String, Double> computeTf(String[] textword) {
double size = textword.length;
HashMap<String, Integer> map = new HashMap();
for (int i = 0; i < textword.length; i++) {
//System.out.println(textword[i]);
if (map.containsKey(textword[i])) {
Integer count = map.get(textword[i]);
map.put(textword[i], count + 1);
} else {
map.put(textword[i], 1);
}
}
HashMap<String, Double> result = new HashMap();
for (Object o : map.keySet()) {
Integer temp = map.get(o);
//System.out.println((String) o + "count..." + temp);
result.put((String) o, temp / size);
//System.out.println((String) o + "tf..." + result.get(o));
}
return result;
}
public void addDic(String path, Map tf) {
//System.out.println(",,,,,,,,,,,,,");
for (Object o : tf.keySet()) {
if (dic.containsKey((String) o)) {
ArrayList list = (ArrayList) dic.get(o);
HashMap map = new HashMap();
map.put(path, (Double) tf.get((String) o));
list.add(map);
dic.put((String) o, list);
} else {
HashMap map = new HashMap();
map.put(path, (Double) tf.get((String) o));
ArrayList list = new ArrayList<Map<String, Double>>();
list.add(map);
dic.put((String) o, list);
}
}
}
public static File[] readData(String path) {
int size = 0;
File[] floderdir = new File(path).listFiles();
ArrayList list = new ArrayList();
for (File f : floderdir) {
// size = size+(int)f.length();
File[] childdir = f.listFiles();
for (File file : childdir) {
list.add(file);
}
}
size = list.size();
File[] fdir = new File[size];
for (int i = 0; i < size; i++) {
fdir[i] = (File) list.get(i);
}
return fdir;
}
public void computeIDF(HashMap<String, List<Map<String, Double>>> map) {
for (String key : map.keySet()) {
List list = map.get(key);
double hasCount = (double) list.size();
double idf = DCOUNT / hasCount;
idfDic.put(key, idf);
}
}
public void ComputeTFIDF() {
for (String filepath : DFdic.keySet()) {
Map filedic = DFdic.get(filepath);
HashMap<String, Double> tfidfPair = tfidfPair = new HashMap();
for (Object key : filedic.keySet()) {
double tf = (Double) filedic.get(key);
double idf = idfDic.get((String) key);
double tfidf = tf* Math.log(idf);
// System.out.println( key+"tf" + tf + "idf" + idf + "tfidf" + tfidf);
tfidfPair.put((String) key, tfidf);
}
// System.out.println(tfidfPair.size());
TFIDFdic.put(filepath, tfidfPair);
}
}
public void toLibData() throws IOException// 轉化成libsvm格式；
{
int count = 0;
// int size =dic.entrySet().size();
List wordList = new ArrayList();
for (String word : dic.keySet()) {
wordList.add(word);
System.out.println("worddic add" + word);
}
// System.out.println("total word is"+wordList.size());
BufferedWriter bw = new BufferedWriter(
new FileWriter(new File(vsmpath)));
/*
* String [] wordList = new String[size]; int num=0; for(String word:
* dic.keySet()) { wordList[num]=word; num++;
* System.out.println("worddic add"+word); }
*/
String vsm = "";
for (String filename : TFIDFdic.keySet()) {
String lable = new File(filename).getParentFile().getName();
Map map = TFIDFdic.get(filename);// 獲取某片文章對應的tfidf
vsm = vsm + lable + " ";
for (int i = 0; i < wordList.size(); i++) {
// System.out.println( "map.."+ map.size());
// String temp =wordList[i];
// System.out.println("temp"+ temp);
String temp = (String) wordList.get(i);
if (map.containsKey(temp)) {
vsm = vsm + i + ":" + map.get(temp) + " ";
// System.out.println(filename + "...." + temp + "...."+
// map.get(temp) + "...");
}
}
count++;
vsm = vsm + "\n";
bw.write(vsm);
vsm = "";
System.out.println("format" + " " + count + " " + filename);
}
System.out.println("begin output");
// BufferedWriter bw = new BufferedWriter(new FileWriter(new
// File(vsmpath)));
// bw.write(vsm);
System.out.println(".............................");
// System.out.println(vsm);
bw.close();
}
}