'nb_words_title'  Number of words in the article's titles
'nb_words_content'  Number of words in the article
'pp_uniq_words'  Proportion of unique words in the article
'pp_stop_words'  Proportion of stop words (i.e. words predefined to be too common to be of use for interpretation or queries, such as 'the', 'a', 'and', etc.)
'pp_uniq_non-stop_words'  Proportion of non-stop words among unique words
'nb_links'  Number of hyperlinks in the article
'nb_outside_links'  Number of hyperlinks pointing to another website
'nb_images'  Number of images in the article
'nb_videos'  Number of videos in the article
'ave_word_length'  Average word length
'nb_keywords'  Number of keywords in the metadata
'category'  Category of the article: 0-Lifestyle, 1-Entertainment, 2-Business, 3-Web, 4-Tech, 5-World
'nb_mina_mink'  Minimum number of share counts among all articles with at least one keyword in common with the article
'nb_mina_maxk'  Minimum number of maximum share counts per keyword
'nb_mina_avek'  Minimum number of average share counts per keyword
'nb_maxa_mink'  Maximum number of minimum share counts per keyword
'nb_maxa_maxk'  Maximum number of share counts among all articles with at least one keyword in common with the article
'nb_maxa_avek'  Maximum number of average share counts per keyword
'nb_avea_mink'  Average number of minimum share counts per keyword
'nb_avea_maxk'  Average number of maximum share counts per keyword
'nb_avea_avek'  Average number of average share counts per keyword
'nb_min_linked'  Minimum number of shares of articles from the same website linked within the article
'nb_max_linked'  Maximum number of shares of articles from the same website linked within the article
'nb_ave_linked'  Average number of shares of articles from the same website linked within the article
'weekday'  Day of the week: 0-Monday, 1-Tuesday, 2-Wednesday, until 6-Sunday
'dist_topic_0'  Distance to topic 0
'dist_topic_1'  Distance to topic 1
'dist_topic_2'  Distance to topic 2
'dist_topic_3'  Distance to topic 3
'dist_topic_4'  Distance to topic 4
'subj'  Subjectivity
'polar'  Sentiment polarity 
'pp_pos_words'  Proportion of positive words in the article
'pp_neg_words'  Proportion of negative words in the article
'pp_pos_words_in_nonneutral'  Proportion of positive words among the non-neutral words of the article
'ave_polar_pos'  Average sentiment polarity of the positive words
'min_polar_pos'  Minimum sentiment polarity of the positive words
'max_polar_pos'  Maximum sentiment polarity of the positive words
'ave_polar_neg'  Average sentiment polarity of the negative words
'min_polar_neg'  Mimimum sentiment polarity of the negative words
'max_polar_neg'  Maximum sentiment polarity of the negative words
'subj_title'  Subjectivity of the title
'polar_title'  Polarity of the title