Merge pull request #39 from cardmagic/add-remove_category

Add remove_category functionality to Bayes classifier

classifier.gemspec

@@ -1,6 +1,6 @@
 Gem::Specification.new do |s|
   s.name        = 'classifier'
-  s.version     = '1.4.0'
+  s.version     = '1.4.1'
   s.summary     = 'A general classifier module to allow Bayesian and other types of classifications.'
   s.description = 'A general classifier module to allow Bayesian and other types of classifications.'
   s.author = 'Lucas Carlson'

lib/classifier/bayes.rb

@@ -139,5 +139,23 @@ def add_category(category)
     end
 
     alias append_category add_category
+
+    #
+    # Allows you to remove categories from the classifier.
+    # For example:
+    #     b.remove_category "Spam"
+    #
+    # WARNING: Removing categories from a trained classifier will
+    # result in the loss of all training data for that category.
+    # Make sure you really want to do this before calling this method.
+    def remove_category(category)
+      category = category.prepare_category_name
+      raise StandardError, "No such category: #{category}" unless @categories.key?(category)
+
+      @categories.delete(category)
+      @category_counts.delete(category)
+      @category_word_count.delete(category)
+      @total_words -= @category_word_count[category].to_i
+    end
   end
 end

test/bayes/bayesian_test.rb

@@ -42,4 +42,56 @@ def test_safari_animals
     assert_equal 'Lion', bayes.classify('lion')
     assert_equal 'Elephant', bayes.classify('elephant')
   end
+
+  def test_remove_category
+    @classifier.train_interesting 'This is interesting content'
+    @classifier.train_uninteresting 'This is uninteresting content'
+
+    assert_equal %w[Interesting Uninteresting].sort, @classifier.categories.sort
+
+    @classifier.remove_category 'Uninteresting'
+
+    assert_equal ['Interesting'], @classifier.categories
+  end
+
+  def test_remove_nonexistent_category
+    assert_raises(StandardError) do
+      @classifier.remove_category 'NonexistentCategory'
+    end
+  end
+
+  def test_remove_category_affects_classification
+    @classifier.train_interesting 'This is interesting content'
+    @classifier.train_uninteresting 'This is uninteresting content'
+
+    assert_equal 'Uninteresting', @classifier.classify('This is uninteresting')
+
+    @classifier.remove_category 'Uninteresting'
+
+    assert_equal 'Interesting', @classifier.classify('This is uninteresting')
+  end
+
+  def test_remove_all_categories
+    @classifier.remove_category 'Interesting'
+    @classifier.remove_category 'Uninteresting'
+
+    assert_empty @classifier.categories
+  end
+
+  def test_remove_and_add_category
+    @classifier.remove_category 'Uninteresting'
+    @classifier.add_category 'Neutral'
+
+    assert_equal %w[Interesting Neutral].sort, @classifier.categories.sort
+  end
+
+  def test_remove_category_preserves_other_category_data
+    @classifier.train_interesting 'This is interesting content'
+    @classifier.train_uninteresting 'This is uninteresting content'
+
+    interesting_classification = @classifier.classify('This is interesting')
+    @classifier.remove_category 'Uninteresting'
+
+    assert_equal interesting_classification, @classifier.classify('This is interesting')
+  end
 end