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

by Andrew Trask

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

In [2]:


In [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]:


Lesson: Develop a Predictive Theory

In [5]:
print("labels.txt \t : \t reviews.txt\n")

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...