Sum or Average of Table Column

index.html.erb

<h3>Result Sets</h3>
<div class="span12" style="width:100%;margin:5px;">

  <% if current.loginable_type != 'Student'  %>
      <%= simple_form_for(result_sets_path, :method =>'get', :html => { :class => 'form-horizontal' }) do %>
          <%= select_tag 'id', options_for_select(@quiz_id), { :prompt => 'Quiz Name'} %>
          <%= select_tag 'student_id', options_for_select(@quiz_student_name), { :prompt => 'Student Name'} %>
          <%= submit_tag 'Submit', :class => 'btn btn-primary' %>
      <% end %>
  <% else %>
      <%= simple_form_for(result_sets_path, :method =>'get', :html => { :class => 'form-horizontal' }) do %>
          <%= select_tag 'id', options_for_select(@quiz_id), { :prompt => 'All Quizzes'} %>
          <% @student_only %>
          <%= submit_tag 'Submit', :class => 'btn btn-primary' %>
      <% end %>
  <% end %>


  <table class="table table-condensed table-bordered table-striped table-responsive">
    <thead>
    <tr>
      <th>Student</th>
      <th>Quiz</th>
      <th>Survey ID</th>
      <th>Result ID</th>
      <th>Possible</th>
      <th>Correct</th>
      <th>Percent</th>
      <th>View</th>
      <% if current.loginable_type != 'Student'  %>
          <th>Delete</th>
      <% end %>
    </tr>
    </thead>
    <% @query.each do |a| %>

        <tbody>
        <tr>
          <td><%= a.student.user.name %></td>
          <td><%= a.survey.name %></td>
          <td><%= a.survey_id %></td>
          <td><%= a.id %></td>
          <td><%= a.total_count.to_f %></td>
          <td><%= a.correct_count.to_f %></td>
          <td><%= a.percent %></td>
          <td><%= link_to " View", result_set_path(a.id), class: 'btn btn-mini  glyphicon glyphicon-eye-open' %></td>
          <% if current.loginable_type != 'Student'  %><td><%= link_to "", result_set_path(a.id), method: :delete, class: 'btn btn-mini btn-danger glyphicon glyphicon-trash', confirm: 'Are you sure?', style: 'margin-left:20%' %></td><% end %>
          <%= @sum %>
        </tr>
        </tbody>
    <% end %>
  </table>


</div>

result_sets_controller.rb

class ResultSetsController < ApplicationController
  before_filter :new

  def index

    @quiz_id = ResultSet.all.map { |u| [u.survey.name, u.survey_id]}.uniq
    @quiz_student_name = ResultSet.all.map { |u| [u.student.user.name, u.student_id]}.uniq

    if current.loginable_type == 'Student'
    @student_only = params[:student_id] = current_user.loginable.id
    end

    runquery = ResultSet
    runquery = runquery.where(:survey_id => params[:id]) if params[:id].present?
    runquery = runquery.where(:student_id => params[:student_id]) if params[:student_id].present?
    runquery = runquery.select('result_sets.*')

    @query = runquery

    @query.each do |a|

      @arr = []
      @actual = []
      @correct = []
      @score = []


      a.serial.to_a.each do |key,value|
        @actual << value
      end

      a.survey.questions.each do |b|

        @id = b.answers
        @id.each do |c|

          if c.correct == true
            @correct = @arr << c.id
          end
        end
      end

      # Virtual Attributes for View
      @score = @correct.collect{|x| "#{x}"} & @actual
      a.correct_count = @score.count.to_f
      a.total_count = @actual.count.to_f
      a.percent = (a.correct_count / a.total_count) * 100

    end

  end

  def new
    @result_set = ResultSet.new
  end

  def create
    @result_set = ResultSet.new(result_set_params)
    @result_set.save!
    if @result_set.save
      redirect_to result_sets_path, notice: "Quiz Completed Successfully"
    else
      redirect_to result_sets_path, notice: "There was a problem, Quiz not saved."
    end
  end

  def show
    @result_set = ResultSet.find(params[:id])

    @actual = []
    @arr = []

    @serial = @result_set.serial

      @result_set.serial.to_a.each do |key,value|
        @actual << value
      end

    @result_set.survey.questions.each do |b|

        @id = b.answers
        @id.each do |c|

          if c.correct == true
            @correct = @arr << c.id
          end
        end
      end

  end

  def destroy
    @result_set = ResultSet.find(params[:id])
    @result_set.destroy
    redirect_to result_sets_url, notice: "Successfully destroyed the user's quiz results."
  end

  private

  def result_set_params
    #params.require(:result_set).permit!
    params.require(:result_set).permit(:id, :student_id, :survey_id, :created_at, :updated_at, survey_attributes: [:id, :name, :created_at, :updated_at, :student_id]).tap do |whitelisted|
      whitelisted[:serial] = params[:result_set][:serial]
      end
  end
end