kmeans.rb

@cluster_centers = [rand_point(), rand_point()]

15.times do
  @clusters = [[], []]

  @posts.each do |post|
    min_distance, min_point = nil, nil

    @cluster_centers.each.with_index do |center, i|
      if distance(center, post) < min_distance
        min_distance = distance(center, post)
        min_point = i
      end
    end

    @clusters[min_point] << post
  end

  @cluster_centers = @clusters.map do |post| 
    average(posts)
  end
end

naive-similar-posts.rb

def similar_posts(post)
  title_keywords = post.title.split(' ')
  Post.all.to_a.sort |post1, post2|
    post1_title_intersection = post1.body.split(' ') & title_keywords
    post2_title_intersection = post2.body.split(' ') & title_keywords

    post2_title_intersection.length <=> post1_title_intersection.length
  end[0..9]
end

post-vector.rb

@posts = Post.all

@words = @posts.map do |p| 
  p.body.split(' ')
end.flatten.uniq

@vectors = @posts.map do |p|
  @words.map do |w| 
    p.body.include?(w) ? 1 : 0 
  end
end

I bet you will get error "ArgumentError: comparison of Fixnum with nil failed" on this line https://gist.github.com/benmcredmond/0dec520b6ab2ce7c59d5#file-kmeans-rb-L10

What is rand_point().

The definition of the method is missing!