Capstone NLP Word Prediction

Analyze the Swiftkey text files (blogs, twitter, and news) and develop a simple Shiny UI for next word prediction in a free form phrase input by user

• Implementation of Dan Jurafsky's n-Gram NLP Interpolation model (Jurafsky Interpolation)
• Building Hash Map indexes between 4-Grams, 3-Grams, 2-Grams, and 1-Grams for fast lookups (primary and foreign key relationships)
• Tradeoff accuracy for speed: Reduce Sparsity, 237894 1-Grams, 347112 Bigrams, 369445 Trigrams, 253621 Quadgrams)
• Code checked in GitHub (NLP Capstone Repo): TextMining.R (training), server.R and ui.R (Shiny App for prediction)

• Cross-references to 4-Grams, 3-Grams, 2-Grams, and 1-Grams stored as integer indexes
• 1-Gram (ugset) stored on disk as RDS with named rows with frequency column
• 2-Gram (bgset) stored on disk as RDS with named rows with frequency, embedded prefix and embedded suffix unigram index columns
• 3-Gram (tgset) stored on disk as RDS with named rows with frequency, embedded prefix bigram and embedded suffix unigram index columns
• 4-Gram (qgset) stored on disk as RDS with named rows with embedded prefix trigram and embedded suffix unigram index columns
• Embedded (n-1)-Gram prefix in a n-Gram is indexed using rownum in (n-1)-Gram

Ranking the candidate words by aggregate probability of n-Gram (higher weights for higher order n-grams). The optimal lambda coefficients obtained by training on known phrases.

\[ P(w1 w2 w3 w4) = l1 * c(w1w2w3w4) / c(w1w2w3) + \] \[ l2 * c(w2w3w4) / c(w2w3) + \] \[ l3 * c(w3w4) / c(w3) + \] \[ l4 * c(w4) / sum of frequencies of all Unigrams, \]

where w4 is the candidate word and the prefix (e.g., (w1 w2 w3) is a embedded trigram, and c() represents the count of a n-gram (frequency column in each n-Gram data set)

Example: In sample phrase, “Hey sunshine, can you follow me and make me the __”, the candidates for prediction: happiest and most are compared by substituting w1 = “make”, w2 = “me”, w3 = “the”, and w4 = (“happiest”,“most”, …) for all candidates and pick the word with highest probability.

• Input text box: Use this box (at the top) to enter a new phrase or edit an existing phrase. This box supports full text navigation and edit capabilities. The text box populates a sample phrase at initialization or a refresh.
• Submit Button: When the text edit is complete, click on this button to initiate the word prediction algorithm
• Progress Bar: The progress of computation to indicate the status of loading/computing.
• Output text box: This box displays the predicted word appended to the original phrase
• Repeat the above three steps for the next phrase
• Initial Wait: The UI takes 20 to 30 seconds to load the training data sets for n-Grams. Please be patient to allow the loading to be complete. The UI is ready to use once the output shows the completion of the sample phrase.