gem 'relationshipanalyzer', :git => 'https://github.com/mono0x/relationshipanalyzer.git'

$ bundle install

require 'MeCab'

class Tagger

  def initialize
    @tagger = MeCab::Tagger.new
  end

  def tokenize(src)
    @tagger.parse(src).force_encoding(Encoding::UTF_8).split("\n").map {|line|
      parts = line.split(',')
      word, category = parts[0].split("\t")
      [ word, category, parts[6] ]
    }.select {|item|
      case
      when item[1] != '名詞'
        false
      when item[2] != '*'
        false
      when item[0].size < 2
        false
      else
        true
      end
    }.map {|item|
      item[0].downcase
    }
  end

end

articles = [
  { :id => ..., :title => ..., :content => ... },
  ...
]

tagger = Tagger.new
items = Hash[*articles.map {|article|
  [ article.id, { :title => tagger.tokenize(article.title), :content => tagger.tokenize(article.content) } ]
}.flatten]
weight = { :title => 3.0, :content => 1.0 }
threshold = 0.1
relationships = RelationshipAnalyzer.relationships(items, weight, threshold)

p relationships[id] # [ { :id => ..., :score => ... }, ... ]