Custom sentiment analysis is hard, but neural network libraries like Keras with built-in LSTM (long, short term memory) functionality have made it feasible. Step into the Data Science Lab with Dr.

Planet Money tries to make a program that reads Donald Trump's tweets and then trades stocks. The first step is training the program to interpret the tweets using something called sentiment analysis.

S&P Dow Jones Indices is launching the S&P 500 Twitter Sentiment Index, which aims to use the Twitter API to track S&P 500 components that are trending in sentiment.