What model was used for sentiment analysis?
Lexicon based word-level  SA.
Social Media users tend to mention entities when reacting to news events. The main purpose of this work is to create entity-centric aggregations of tweets on a daily basis. By applying topic modeling and sentiment analysis, we create data visualization insights about current events and people reactions to those events from an entity-centric perspective.
Entities play a central role in the interplay between social media and online news BIBREF0 . Everyday millions of tweets are generated about local and global news, including people reactions and opinions regarding the events displayed on those news stories. Trending personalities, organizations, companies or geographic locations are building blocks of news stories and their comments. We propose to extract entities from tweets and their associated context in order to understand what is being said on Twitter about those entities and consequently to create a picture of people reactions to recent events. With this in mind and using text mining techniques, this work explores and evaluates ways to characterize given entities by finding: (a) the main terms that define that entity and (b) the sentiment associated with it. To accomplish these goals we use topic modeling BIBREF1 to extract topics and relevant terms and phrases of daily entity-tweets aggregations, as well as, sentiment analysis BIBREF2 to extract polarity of frequent subjective terms associated with the entities. Since public opinion is, in most cases, not constant through time, this analysis is performed on a daily basis. Finally we create a data visualization of topics and sentiment that aims to display these two dimensions in an unified and intelligible way. The combination of Topic Modeling and Sentiment Analysis has been attempted before: one example is a model called TSM - Topic-Sentiment Mixture Model BIBREF3 that can be applied to any Weblog to determine a correlation between topic and sentiment. Another similar model has been proposed proposed BIBREF4 in which the topic extraction is achieved using LDA, similarly to the model that will be presented. Our work distinguishes from previous work by relying on daily entity-centric aggregations of tweets to create a meta-document which will be used as input for topic modeling and sentiment analysis.