gistfile1.rb

scope :by_rating, :lambda do |order|
    order ||= "ASC"
    previous_scope = ?

    all_scores = previous_scope.where("num_scores > ?", 0).sum('score')
    num_of_all_scores = previous_scope.where("num_scores > ?", 0).sum('num_scores')
    site_avg = all_scores.to_f / num_of_all_scores.to_f
    site_avg = 0 if num_of_all_scores <= 0 # this is the reason I'd like to do it this way instead of the normal way
    min_votes = 5
    previous_scope.where("num_scores > ?", 0).order("((num_scores / (num_scores + #{min_votes})) * (score / num_scores) + (#{min_votes} / (num_scores + #{min_votes})) * #{site_avg}) #{order}")
end