Instead of the entities_url (boolean), entities_hashtags(int), entities_mentions(int) and entities_media(int) members of the feature vector, lets have five double members: fraction_text, fraction_url, fraction_media, fraction_mention, fraction_hashtag which should add up to one and indicate what proportion of the tweet (in terms of characters) is made up of those components.

As far as position within the tweet is concerned, we only calculate that for the first URL in the tweet