require 'pp'
ary = %w(w1 w2 w3 w4 w2 w3 w1 w1 w5 w2 w3 w4)
zero = ary.uniq.inject(Hash.new){|h,w| h[w] = 0 ; h }
window = 6
hout = Hash.new
ary.each_with_index do |key,i|
　(hout[key] = zero.dup).delete(key) unless hout.key?(key)
　ary[i+1,window].select{|e| e != key }.each {|word| hout[key][word] += 1 }
end