[DOC] Documentation for TFIDF.

analysis/functions.py

@@ -245,17 +245,21 @@ def get_cooc(request=None, corpus_id=None, cooc_id=None, type='node_link', n=150
 
 
 def tfidf(corpus, document, ngram):
+    '''
+    Compute TF-IDF (Term Frequency - Inverse Document Frequency)
+    See: http://en.wikipedia.org/wiki/Tf%E2%80%93idf
+    '''
     try:
         occurences_of_ngram = Node_Ngram.objects.get(node=document, ngram=ngram).weight
         ngrams_by_document = sum([ x.weight for x in Node_Ngram.objects.filter(node=document)])
         term_frequency = occurences_of_ngram / ngrams_by_document
     
         xx = Node.objects.filter(parent=corpus, type=NodeType.objects.get(name="Document")).count()
-        yy = Node_Ngram.objects.filter(ngram=ngram).count()
-        inverse_d_frequency= log(xx/yy)
+        yy = Node_Ngram.objects.filter(ngram=ngram).count() # filter: ON node.parent=corpus
+        inverse_document_frequency= log(xx/yy)
         
         # result = tf * idf
-        result = term_frequency * inverse_d_frequency
+        result = term_frequency * inverse_document_frequency
     except Exception as error:
         print(error, ngram)
         result = 0