Add a prioriProbs method and test case.

Author: felipexw

.gitignore

@@ -1,3 +1,4 @@
 .idea/
 Recomenda-Engine.iml
-target/
+target/
+knn-java-library.iml

src/main/java/com/github/felipexw/classifier/bayes/MultinomialNaiveBayesClassifier.java

@@ -4,12 +4,15 @@
 import com.github.felipexw.classifier.CrossValidateClassifier;
 import com.github.felipexw.types.LabeledTrainingInstance;
 import com.github.felipexw.types.PredictedInstance;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 /**
  * Created by felipe.appio on 29/08/2016.
  */
-public class MultinomialNaiveBayesClassifier implements Classifier, CrossValidateClassifier{
+public class MultinomialNaiveBayesClassifier extends NaiveBayes
+ implements Classifier, CrossValidateClassifier {
 
  @Override public void train(List<LabeledTrainingInstance> instances) {
 
@@ -26,4 +29,19 @@ public class MultinomialNaiveBayesClassifier implements Classifier, CrossValida
  @Override public void train(List<LabeledTrainingInstance> instances, int k) {
 
  }
+
+ @Override
+ public Map<String, Integer> calculateAPrioriProbs(List<LabeledTrainingInstance> instanceList) {
+ Map<String, Integer> probs = new HashMap<>();
+
+ for (LabeledTrainingInstance instance : instanceList) {
+ if (!probs.containsKey(instance.getLabel())) {
+ probs.put(instance.getLabel(), 1);
+ } else {
+ probs.put(instance.getLabel(), probs.get(instance.getLabel()) + 1);
+ }
+ }
+
+ return probs;
+ }
 }

src/main/java/com/github/felipexw/classifier/bayes/NaiveBayes.java

@@ -0,0 +1,12 @@
+package com.github.felipexw.classifier.bayes;
+
+import com.github.felipexw.types.LabeledTrainingInstance;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Created by felipe.appio on 29/08/2016.
+ */
+public abstract class NaiveBayes {
+ public abstract Map<String, Integer> calculateAPrioriProbs (List<LabeledTrainingInstance> instanceList);
+}

src/test/java/MultinomialNaiveBayesClassifierTest.java

@@ -1,11 +1,45 @@
+import com.github.felipexw.classifier.Classifier;
+import com.github.felipexw.classifier.bayes.MultinomialNaiveBayesClassifier;
+import com.github.felipexw.classifier.bayes.NaiveBayes;
+import com.github.felipexw.types.LabeledTrainingInstance;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import org.junit.Before;
 import org.junit.Test;
 
+import static com.google.common.truth.Truth.*;
+
 /**
  * Created by felipe.appio on 29/08/2016.
  */
 public class MultinomialNaiveBayesClassifierTest {
 
+ private NaiveBayes naiveBayesClassifier;
+
+ @Before
+ public void setUp() {
+ naiveBayesClassifier = new MultinomialNaiveBayesClassifier();
+ }
+
  @Test
- public void it_should_fail(){
+ public void it_should_calculate_a_priori_probs() {
+ String negativeLabel = "negative";
+ String positiveLabel = "positive";
+
+ List<LabeledTrainingInstance> training =
+ Arrays.asList(new LabeledTrainingInstance(new double[] {2}, negativeLabel),
+ new LabeledTrainingInstance(new double[] {2}, negativeLabel),
+ new LabeledTrainingInstance(new double[] {2}, positiveLabel));
+
+ Map<String, Integer> probs = naiveBayesClassifier.calculateAPrioriProbs(training);
+
+ assertThat(probs.get(negativeLabel))
+ .isEqualTo(2);
+ assertThat(probs.get(positiveLabel))
+ .isEqualTo(1);
  }
+
+
 }