Sentiment Classification & How To "Frame Problems" for a Neural Network

by Andrew Trask

Twitter: @iamtrask
Blog: http://iamtrask.github.io

What You Should Already Know

neural networks, forward and back-propagation
stochastic gradient descent
mean squared error
and train/test splits

Where to Get Help if You Need it

Re-watch previous Udacity Lectures
Leverage the recommended Course Reading Material - Grokking Deep Learning (40% Off: traskud17)
Shoot me a tweet @iamtrask

Tutorial Outline:

Intro: The Importance of "Framing a Problem"

Curate a Dataset
Developing a "Predictive Theory"
PROJECT 1: Quick Theory Validation

Transforming Text to Numbers
PROJECT 2: Creating the Input/Output Data

Putting it all together in a Neural Network
PROJECT 3: Building our Neural Network

Understanding Neural Noise
PROJECT 4: Making Learning Faster by Reducing Noise

Analyzing Inefficiencies in our Network
PROJECT 5: Making our Network Train and Run Faster

Further Noise Reduction
PROJECT 6: Reducing Noise by Strategically Reducing the Vocabulary

Analysis: What's going on in the weights?

Lesson: Curate a Dataset



In [1]:

    
def pretty_print_review_and_label(i):
    print(labels[i] + "\t:\t" + reviews[i][:80] + "...")

g = open('reviews.txt','r') # What we know!
reviews = list(map(lambda x:x[:-1],g.readlines()))
g.close()

g = open('labels.txt','r') # What we WANT to know!
labels = list(map(lambda x:x[:-1].upper(),g.readlines()))
g.close()



In [2]:

    
len(reviews)









    Out[2]:





25000



In [3]:

    
reviews[0]









    Out[3]:





'bromwell high is a cartoon comedy . it ran at the same time as some other programs about school life  such as  teachers  . my   years in the teaching profession lead me to believe that bromwell high  s satire is much closer to reality than is  teachers  . the scramble to survive financially  the insightful students who can see right through their pathetic teachers  pomp  the pettiness of the whole situation  all remind me of the schools i knew and their students . when i saw the episode in which a student repeatedly tried to burn down the school  i immediately recalled . . . . . . . . . at . . . . . . . . . . high . a classic line inspector i  m here to sack one of your teachers . student welcome to bromwell high . i expect that many adults of my age think that bromwell high is far fetched . what a pity that it isn  t   '



In [4]:

    
labels[0]









    Out[4]:





'POSITIVE'

Lesson: Develop a Predictive Theory



In [5]:

    
print("labels.txt \t : \t reviews.txt\n")
pretty_print_review_and_label(2137)
pretty_print_review_and_label(12816)
pretty_print_review_and_label(6267)
pretty_print_review_and_label(21934)
pretty_print_review_and_label(5297)
pretty_print_review_and_label(4998)









    



labels.txt 	 : 	 reviews.txt

NEGATIVE	:	this movie is terrible but it has some good effects .  ...
POSITIVE	:	adrian pasdar is excellent is this film . he makes a fascinating woman .  ...
NEGATIVE	:	comment this movie is impossible . is terrible  very improbable  bad interpretat...
POSITIVE	:	excellent episode movie ala pulp fiction .  days   suicides . it doesnt get more...
NEGATIVE	:	if you haven  t seen this  it  s terrible . it is pure trash . i saw this about ...
POSITIVE	:	this schiffer guy is a real genius  the movie is of excellent quality and both e...