Created task to generate pajek tags graph

Signed-off-by: Israel Barreto Sant'Anna <ibsa14@inf.ufpr.br>

lib/tasks/tag_clustering.rake

+require 'json'
+namespace :tag do
+  desc 'Generate tag clusters'
+  task generate_clusters: :environment do
+    hash = {}
+    edges_total = 0
+    outDIR = "tmp/"
+
+    def swap(a, b)
+      tmp = a
+      a = b
+      b = tmp
+    end
+
+    LearningObject.all.each do |lo|
+      # for each lo, count tags and tag pairs and add to hash
+      # if id1 <= id2
+      # hash[id1][id2] will equal how many times tags with id1 and id2 appear together on a LO
+      lo.tags.each.with_index do |t, i|
+        hash[t.id] = {} if hash[t.id].nil?
+        lo.tags.drop(i+1).each do |t2|
+          if t.id > t2.id
+            swap(t, t2)
+            hash[t.id] = {} if hash[t.id].nil?
+          end
+          if hash[t.id][t2.id].nil?
+            hash[t.id][t2.id] = 0
+          end
+          hash[t2.id] = {} if hash[t2.id].nil?
+
+          hash[t2.id][t2.id] = 0 if hash[t2.id][t2.id].nil?
+          hash[t2.id][t2.id] += 1
+          hash[t.id][t.id] = 0 if hash[t.id][t.id].nil?
+          hash[t.id][t.id] += 1
+
+          hash[t.id][t2.id] += 1
+        end
+      end
+    end
+
+    File.open(outDIR + "pajek.net", "w+") do |f|
+      f << "*Vertices #{Tag.all.size}\n"
+      # tags = Tag.all.to_ary
+      tag_index = {}
+      Tag.all.each_with_index do |t,i|
+        f << "#{i+1} \"#{t.name}\"\n"
+        tag_index[t.id] = i+1
+      end
+
+      f << "*Edges #{edges_total}\n"
+
+      hash.each do |id1, ids2Hash|
+        ids2Hash.each do |id2, value|
+          if id1 != id2
+            f << "#{tag_index[id1]} #{tag_index[id2]} #{hash[id1][id2].to_f/(hash[id1][id1].to_f+hash[id2][id2].to_f)}\n"
+          end
+        end
+      end
+    end
+  end
+end