Combining Machine Learning classifier with NLTK Vader for Sentiment Analysis
Interesting approach, but the whole purpose of NLTK Vader is to have a pre-trained model. After all, NLTK Vader was manually (!) labeled.

I just tested Google vs. NLTK Vader on "I did not hate this movie" (negations are notoriously hard to catch for an algorithm) and NLTK Vader did much better than Google. NLTK Vader scored it kind of positive (0.45) while Google scored it negatively (-0.6).

Interesting ... :-)

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Good luck!