1 files changed, 56 insertions, 0 deletions
diff --git a/lib/classification.rb b/lib/classification.rb
new file mode 100644
index 0000000..f6c9b11
--- /dev/null
+++ b/lib/classification.rb
@@ -0,0 +1,56 @@
+module OpenTox
+  module Algorithm
+    
+    class Classification
+
+      # Classification with majority vote from neighbors weighted by similarity
+      # @param [Hash] params Keys `:activities, :sims, :value_map` are required
+      # @return [Numeric] A prediction value.
+      def self.weighted_majority_vote(neighbors)
+
+        return {:prediction => nil, :confidence => nil} if neighbors.empty?
+
+        neighbor_contribution = 0.0
+        confidence_sum = 0.0
+        confidence = 0.0
+        prediction = nil
+
+        $logger.debug "Weighted Majority Vote Classification."
+
+        values = neighbors.collect{|n| n[1]}.uniq
+        neighbors.each do |neighbor|
+          neighbor_weight = neighbor[2]
+          activity = values.index(neighbor[1]) + 1 # map values to integers > 1
+          neighbor_contribution += activity * neighbor_weight
+          if values.size == 2 # AM: provide compat to binary classification: 1=>false 2=>true
+            case activity
+            when 1
+              confidence_sum -= neighbor_weight
+            when 2
+              confidence_sum += neighbor_weight
+            end
+          else
+            confidence_sum += neighbor_weight
+          end
+        end
+        if values.size == 2 
+          if confidence_sum >= 0.0
+            prediction = values[1]
+          elsif confidence_sum < 0.0
+            prediction = values[0] 
+          end
+        else 
+          prediction = (neighbor_contribution/confidence_sum).round  # AM: new multinomial prediction
+        end 
+
+        $logger.debug "Prediction: '" + prediction.to_s + "'." unless prediction.nil?
+        confidence = (confidence_sum/neighbors.size).abs 
+        $logger.debug "Confidence: '" + confidence.to_s + "'." unless prediction.nil?
+        return {:prediction => prediction, :confidence => confidence.abs}
+      end
+
+    end
+
+  end
+end
+