add API call for median votes per session

app/controllers/questions_controller.rb

@@ -84,6 +84,13 @@ def export
 #    export_format = params[:export_format] #CSV always now, could expand to xml later
   end
 
+  def median_votes_per_session
+    @question = current_user.questions.find(params[:id])
+    respond_to do |format|
+    	format.xml{ render :xml => {:median => @question.median_votes_per_session}.to_xml and return}
+    end
+  end
+
   def object_info_by_visitor_id
 
     object_type = params[:object_type]

app/models/question.rb

@@ -1,5 +1,6 @@
 class Question < ActiveRecord::Base
   require 'set'
+  include Utility
   extend ActiveSupport::Memoizable
 
   belongs_to :creator, :class_name => "Visitor", :foreign_key => "creator_id"
@@ -50,7 +51,17 @@ def create_choices_from_ideas
   def item_count
     choices.size
   end
-
+
+  # returns array of hashes where each has has voter_id and total keys
+  def votes_per_session
+    self.votes.find(:all, :select => 'voter_id, count(*) as total', :group => :voter_id).map { |v| {:voter_id => v.voter_id, :total => v.total.to_i} }
+  end
+
+  def median_votes_per_session
+    totals = self.votes_per_session.map { |v| v[:total] }
+    return median(totals)
+  end
+
   def choose_prompt(options = {})
 
           # if there is one or fewer active choices, we won't be able to find a prompt

config/routes.rb

@@ -6,6 +6,7 @@
   map.resources :questions, :except => [:edit, :destroy],
                             :member => {:object_info_totals_by_date => :get, 
 	  				:object_info_by_visitor_id => :get, 
+					    :median_votes_per_session => :get,
                                         :export => :post} , 
 			    :collection => {:all_num_votes_by_visitor_id => :get, 
 					    :all_object_info_totals_by_date => :get,

lib/utility.rb

@@ -0,0 +1,12 @@
+module Utility
+  def mean(array)
+    array.inject(0) { |sum, x| sum += x } / array.size.to_f
+  end
+
+  def median(array, already_sorted=false)
+    return nil if array.empty?
+    array = array.sort unless already_sorted
+    m_pos = array.size / 2
+    return array.size % 2 == 1 ? array[m_pos] : mean(array[m_pos-1..m_pos])
+  end
+end

spec/integration/questions_spec.rb

@@ -10,6 +10,15 @@
     end
   end
 
+  describe "GET 'median_votes_per_session'" do
+    it "should return the median" do
+      Factory.create(:vote, :question => @questions.first)
+      get_auth median_votes_per_session_question_path(@questions.first, :format => 'xml')
+      response.should be_success
+      response.body.should have_tag("median", :text => "1")
+    end
+  end
+
   describe "GET 'index'" do
     it "should return an array of questions" do
       get_auth questions_path(:format => 'xml')

spec/models/question_spec.rb

@@ -22,6 +22,15 @@
     @question.choices.active.reload.size.should == 2
   end
 
+  it "should report median votes per session" do
+    aoiquestion = Factory.create(:aoi_question)
+    prompt = aoiquestion.prompts.first
+    Factory.create(:vote, :question => aoiquestion, :prompt => prompt)
+    Factory.create(:vote, :question => aoiquestion, :prompt => prompt)
+    aoiquestion.votes_per_session.should == [{:voter_id => aoiquestion.creator.id, :total => 2}]
+    aoiquestion.median_votes_per_session.should == 2
+  end
+
   it "should create a new instance given valid attributes" do
     # Factory.attributes_for does not return associations, this is a good enough substitute
     Question.create!(Factory.build(:question).attributes.symbolize_keys)