diff --git a/sentiment_analysis.py b/sentiment_analysis.py
index 9d114d6..19b6e0d 100644
--- a/sentiment_analysis.py
+++ b/sentiment_analysis.py
@@ -3,7 +3,10 @@ import json
 import sentiment_analysis_functions as sfun
 
 # installation
+# import nltk
 # nltk.download('punkt')
+# nltk.download('wordnet')
+# nltk.download('stopwords')
 
 from sklearn.feature_extraction.text import CountVectorizer
 from sklearn.naive_bayes import MultinomialNB
@@ -32,6 +35,12 @@ if __name__ == '__main__':
     print("Nb of training reviews - positive:", len(train_positive_reviews), "negative:", len(train_negative_reviews))
     print("Nb of test reviews - positive:", len(test_positive_reviews), "negative:", len(test_negative_reviews))
     
-    xx = sfun.tokenize(train_positive_reviews)
-    xx[0]
+    x0 = sfun.tokenize(train_positive_reviews)
+    x1 = sfun.norm_stemming(x0)
+    x2 = sfun.norm_lemmatize(x0)
+    
+    x11 = sfun.select_freq(x1)
+    x21 = sfun.select_freq(x2)
 
+    x12 = sfun.select_rem_stopwords(x1)
+    x22 = sfun.select_rem_stopwords(x2)
\ No newline at end of file
diff --git a/sentiment_analysis_functions.py b/sentiment_analysis_functions.py
index dd3ac92..979e85b 100644
--- a/sentiment_analysis_functions.py
+++ b/sentiment_analysis_functions.py
@@ -8,35 +8,83 @@ Created on Sun Oct 27 17:16:54 2019
 
 import nltk
 import re
+from collections import defaultdict
 
 ## Normalisation
     
 def tokenize(reviews):
+    tokenizer = nltk.tokenize.ToktokTokenizer()
     tokenized_reviews = []
     for review in reviews:
         # Plusieurs fin de phrases étaient représentées par deux espaces ou plus.
         review = re.sub(r"\s{2,}",". ",review)
+        review = str.lower(review)
         tokenized_sentences = []
         sentences = nltk.sent_tokenize(review)
         for sentence in sentences:
-            sentence_tokens = nltk.word_tokenize(sentence)
+            sentence_tokens = tokenizer.tokenize(sentence)
+            # Suppression de la ponctuation
+            for token in sentence_tokens:
+                if token in "?:!.,;":
+                    sentence_tokens.remove(token)
             tokenized_sentences.append(sentence_tokens)
         tokenized_reviews.append(tokenized_sentences)
     return tokenized_reviews
 
 def norm_stemming(tokenized_reviews):
-    return 0
+    porter = nltk.PorterStemmer()
+    stemmed_reviews = []
+    for review in tokenized_reviews:
+        stemmed_review = []
+        for sentence in review:
+            stemmed_tokens = [porter.stem(token) for token in sentence]
+            stemmed_review.append(stemmed_tokens)
+        stemmed_reviews.append(stemmed_review)
+    return stemmed_reviews
 
 def norm_lemmatize(tokenized_reviews):
-    return 0
+    wnl = nltk.WordNetLemmatizer()
+    normalized_reviews = []
+    for review in tokenized_reviews:
+        normalized_review = []
+        for sentence in review:
+            # Lemmatisation au verbe et non au nom
+            normalized_tokens = [wnl.lemmatize(token, pos="v") for token in sentence]
+            normalized_review.append(normalized_tokens)
+        normalized_reviews.append(normalized_review)
+    return normalized_reviews
 
 ## Feature selection
-
-def select_freq(reviews):
-    return 0
     
-def select_rem_stopwords(reviews):
-    return 0
+def dict_frequency(norm_reviews):
+    tokens_frequency = defaultdict(int)
+    for review in norm_reviews:
+        for sentence in review:
+            for token in sentence:
+                tokens_frequency[token] += 1
+    return tokens_frequency
+
+def select_freq(norm_reviews):
+    tokens_frequency = dict_frequency(norm_reviews)
+    norm_reviews_freq3 = [
+     [
+      [token for token in sentence if tokens_frequency[token] > 3] 
+      for sentence in review
+      ] 
+     for review in norm_reviews
+     ]
+    return norm_reviews_freq3
+    
+def select_rem_stopwords(norm_reviews):
+    sws = set(nltk.corpus.stopwords.words('english'))
+    norm_reviews_stoprem = [
+     [
+      [token for token in sentence if token not in sws] 
+      for sentence in review
+      ] 
+     for review in norm_reviews
+     ]
+    return norm_reviews_stoprem
     
 def select_open_class(reviews):
     return 0