1 files changed, 33 insertions, 0 deletions
diff --git a/src/Chapter4/tweetlda/PorterStemmer.java b/src/Chapter4/tweetlda/PorterStemmer.java
new file mode 100644
index 0000000..1a7149e
--- /dev/null
+++ b/src/Chapter4/tweetlda/PorterStemmer.java
@@ -0,0 +1,33 @@
+package tweetlda;
+
+import cc.mallet.pipe.Pipe;
+import cc.mallet.types.Instance;
+import cc.mallet.types.TokenSequence;
+
+public class PorterStemmer extends Pipe {
+
+	private static final long serialVersionUID = 154100332101873830L;
+
+	public Instance pipe(Instance carrier){
+		TokenSequence ts = (TokenSequence) carrier.getData();
+		String word;
+		Stemmer s;
+		
+		for(int i = 0; i < ts.size(); i++){
+			word = ts.get(i).getText();
+			//stem the word
+			s = new Stemmer();
+			for(char ch : word.toCharArray()){
+				if(Character.isLetter(ch)){
+					s.add(ch);
+				}
+			}
+			s.stem();
+			ts.get(i).setText(s.toString());
+		}
+		carrier.setData(ts);
+
+		return carrier;
+	}
+
+}