Algorithm to determine how positive or negative a statement/text is

Question

I need an algorithm to determine if a sentence, paragraph or article is negative or positive in tone... or better yet, how negative or positive.

For instance:

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Answer 1

As pointed out, this comes under sentiment analysis under natural language processing.
Afaik GATE doesn't have any component that does sentiment analysis.
In my experience, I have implemented an algorithm which is an adaptation of the one in the paper 'Recognizing Contextual Polarity in Phrase-Level Sentiment Analysis' by Theresa Wilson, Janyce Wiebe, Paul Hoffmann (this) as a GATE plugin, which gives reasonable good results. It could help you if you want to bootstrap the implementation.