word.java

complete bayesian spam filter (java source code)

/* Daniel Shiffman               */
/* Bayesian Spam Filter Example  */
/* Programming from A to Z       */
/* Spring 2006                   */
/* http://www.shiffman.net       */
/* [e-mail]       */

// This class describes a word
// and the various probabilities associated with that word

package bayes;

public class Word {
	private String word;    // The String itself
	private int countBad;   // The total times it appears in "bad" messages 
	private int countGood;  // The total times it appears in "good" messages
	private float rBad;     // bad count / total bad words
	private float rGood;    // good count / total good words
	private float pSpam;    // probability this word is Spam
	
	// Create a word, initialize all vars to 0
	public Word(String s) {
		word = s;
		countBad = 0;
		countGood = 0;
		rBad = 0.0f;
		rGood = 0.0f;
		pSpam = 0.0f;
	}
	
	// Increment bad counter
	public void countBad() {
		countBad++;
	}

	// Increment good counter
	public void countGood() {
		countGood++;
	}

	// Computer how often this word is bad
	public void calcBadProb(int total) {
		if (total > 0) rBad = countBad / (float) total;
	}
	
	// Computer how often this word is good
	public void calcGoodProb(int total) {
		if (total > 0) rGood = 2*countGood / (float) total; // multiply 2 to help fight against false positives (via Graham)
	}

	// Implement bayes rules to computer how likely this word is "spam"
	public void finalizeProb() {
		if (rGood + rBad > 0) pSpam = rBad / (rBad + rGood);
		if (pSpam < 0.01f) pSpam = 0.01f;
		else if (pSpam > 0.99f) pSpam = 0.99f;
	}

	
	// The "interesting" rating for a word is
	// How different from 0.5 it is
	public float interesting() {
		return Math.abs(0.5f - pSpam);
	}
	
	// Some getters and setters	
	public float getPGood() {
		return rGood;
	}

	public float getPBad() {
		return rBad;
	}
	
	public float getPSpam() {
		return pSpam;
	}

	public void setPSpam(float f) {
		pSpam = f;
	}

	public String getWord() {
		return word;
	}
	
}