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Questions and Answers
After creating a Bag of Words model, what is a common next step to examine the model's features?
After creating a Bag of Words model, what is a common next step to examine the model's features?
After creating numeric features using Bag of Words and having sentiment labels, what is a typical method used for classification?
After creating numeric features using Bag of Words and having sentiment labels, what is a typical method used for classification?
When applying a Random Forest classifier, what impact does increasing the number of trees typically have on the model?
When applying a Random Forest classifier, what impact does increasing the number of trees typically have on the model?
For the assignment task, how should the trained Random Forest be used with the test dataset?
For the assignment task, how should the trained Random Forest be used with the test dataset?
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When submitting the results of the Random Forest classifier prediction on the test dataset, what file format is requested?
When submitting the results of the Random Forest classifier prediction on the test dataset, what file format is requested?
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What does a sentiment score of 0 indicate in the IMDB movie review dataset?
What does a sentiment score of 0 indicate in the IMDB movie review dataset?
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What is the purpose of setting quoting=3
when reading the labeled training data?
What is the purpose of setting quoting=3
when reading the labeled training data?
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If a movie review in the IMDB dataset has a rating of 6, what would its corresponding sentiment score be?
If a movie review in the IMDB dataset has a rating of 6, what would its corresponding sentiment score be?
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What is the primary purpose of using the Beautiful Soup library in the context of the movie review data?
What is the primary purpose of using the Beautiful Soup library in the context of the movie review data?
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What does the delimiter='\t'
argument specify when reading the labeled training data?
What does the delimiter='\t'
argument specify when reading the labeled training data?
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Why might punctuation marks be retained in sentiment analysis, as opposed to being removed?
Why might punctuation marks be retained in sentiment analysis, as opposed to being removed?
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In the given dataset, how many labeled movie reviews are dedicated to the training set?
In the given dataset, how many labeled movie reviews are dedicated to the training set?
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What is the primary role of the re
package in data cleaning for the sentiment analysis task described in the text?
What is the primary role of the re
package in data cleaning for the sentiment analysis task described in the text?
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What is the primary purpose of the re.sub()
function mentioned in the text?
What is the primary purpose of the re.sub()
function mentioned in the text?
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What does 'tokenization' refer to in the context of NLP, as described in the text?
What does 'tokenization' refer to in the context of NLP, as described in the text?
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What is a stop word?
What is a stop word?
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Why is it beneficial to convert the list of stop words to a set before removing them from text?
Why is it beneficial to convert the list of stop words to a set before removing them from text?
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In the context of cleaning text data, what is the purpose of joining words back into one paragraph after removing stop words?
In the context of cleaning text data, what is the purpose of joining words back into one paragraph after removing stop words?
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Besides re.sub()
, what other processing steps are mentioned as part of cleaning movie reviews?
Besides re.sub()
, what other processing steps are mentioned as part of cleaning movie reviews?
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What does the code do after the stop word removal and other text cleaning processes?
What does the code do after the stop word removal and other text cleaning processes?
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Why is creating a function necessary for cleaning movie review data?
Why is creating a function necessary for cleaning movie review data?
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What does the Bag of Words model primarily do?
What does the Bag of Words model primarily do?
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In the example given, what is the feature vector for sentence 1 ('The cat sat on the hat')?
In the example given, what is the feature vector for sentence 1 ('The cat sat on the hat')?
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Why is it necessary to choose a maximum vocabulary size when using the Bag of Words model with a large dataset?
Why is it necessary to choose a maximum vocabulary size when using the Bag of Words model with a large dataset?
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What does the CountVectorizer do?
What does the CountVectorizer do?
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If the vocabulary is {the, quick, brown, fox, jumps}, and the sentence is 'the quick fox jumps over the lazy dog', what will be the correct feature vector?
If the vocabulary is {the, quick, brown, fox, jumps}, and the sentence is 'the quick fox jumps over the lazy dog', what will be the correct feature vector?
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What would be a plausible feature vector if there are 8 words total in the vocabulary, and only one appears 3 times in a document, another word appears twice, and the rest appear once or not at all?
What would be a plausible feature vector if there are 8 words total in the vocabulary, and only one appears 3 times in a document, another word appears twice, and the rest appear once or not at all?
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Which of these is NOT a typical step for preparing text for a Bag of Words model?
Which of these is NOT a typical step for preparing text for a Bag of Words model?
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What happens after the training reviews are cleaned?
What happens after the training reviews are cleaned?
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Flashcards
Labeled Training Data
Labeled Training Data
A collection of reviews with a positive or negative sentiment label.
Test Set
Test Set
A set of reviews used to evaluate the performance of a trained sentiment analysis model.
ID
ID
A unique identifier assigned to each movie review in the dataset.
Sentiment Score
Sentiment Score
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Review Text
Review Text
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Text Preprocessing
Text Preprocessing
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Beautiful Soup
Beautiful Soup
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re
re
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Feature Engineering
Feature Engineering
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Bag of Words Model
Bag of Words Model
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Random Forest
Random Forest
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Test Dataset
Test Dataset
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Sentiment Prediction
Sentiment Prediction
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re.sub('[^a-zA-Z]', ' ', review)
re.sub('[^a-zA-Z]', ' ', review)
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Tokenization
Tokenization
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Stop Words
Stop Words
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NLTK (Natural Language Toolkit)
NLTK (Natural Language Toolkit)
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Removing stop words
Removing stop words
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Bag of Words
Bag of Words
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Reusable Function
Reusable Function
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Vocabulary
Vocabulary
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Feature Vector
Feature Vector
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Maximum Vocabulary Size
Maximum Vocabulary Size
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CountVectorizer
CountVectorizer
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Scikit-learn
Scikit-learn
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Study Notes
Introduction to Natural Language Processing - Sentiment Analysis Case Study
- The case study focuses on sentiment analysis using 50,000 IMDB movie reviews.
- The dataset includes a training set (25,000 reviews) and a test set (25,000 reviews).
- Sentiment is binary: IMDB ratings less than 5 = 0 (negative), 5 or greater = 1 (positive).
- The training data does not include any reviews from the test set.
- Data fields are unique ID (
id
), sentiment label (1 for positive, 0 for negative), and review text.
Reading the Data
- The
labeled TrainData.tsv
file contains tab-separated data (id, sentiment, review). - Use
pandas
to read the file into a dataframe. header = 0
specifies the first row contains column names.delimiter = "\t"
indicates tab as the column separator.quoting = 3
tells Python to ignore double quotes.
Reading the Data - Verification
train.shape
returns the dimensions (rows, columns) of the dataframe, confirming the correct size of the data.train.columns.values
shows the column names.train.iloc[0]
displays the first row of the dataframe for manual verification.
Reading the Data - Review Examples
- The reviews are text-based and can provide insight into the sentiment expressed.
- A few example reviews are shown, demonstrating the content.
Data Cleaning and Text Preprocessing
- Remove HTML tags using
BeautifulSoup
package. - The steps for cleaning the data (removing HTML tags, punctuation marks and digits) can be performed in a sequence.
Dealing with Punctuation, Numbers and Stopwords:
- Data cleaning considers punctuation and numbers.
- Removing punctuation and numbers uses a regular expression.
- Stopwords, frequently occurring words with little meaning, are identified and removed (e.g., "the","a").
- Python's
nltk
library can be used to get a list of English stopwords.
Dealing with Punctuation, Numbers and Stopwords: (Function)
review_to_words()
function processes reviews for punctuation removal.- Stopwords are converted to a set for optimized searching.
- The function returns processed reviews.
Dealing with Punctuation, Numbers and Stopwords: (Loop for processing)
clean_train_reviews
list is created to hold processed reviews.- A loop iterates through the entire training dataset and applies the
review_to_words()
function to each element in the dataset, preserving it in theclean_train_reviews
list.
Creating Features From A Bag Of Words (Using Scikit-Learn)
- The Bag-of-Words model counts word occurrences in each document to create numeric features.
- Vocabulary is generated from training set documents.
CountVectorizer
creates feature vectors from the cleaned reviews.- A maximum vocabulary size (5000 most frequent words) is frequently used to limit the feature vector size.
Apply ML Algorithm
- A
RandomForestClassifier
is initialized with 100 trees. - The trained model (
forest
) is used to predict sentiment on new data.
Assignment Task
- Use the trained
RandomForest
model to predict sentiment on a separate test dataset. - Format the output as a dataframe (.csv or .xlsx).
- Crucial: Do not fit the model to the test data. Only use the trained model from the training set for prediction.
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Description
Test your knowledge of sentiment analysis using the Bag of Words model and Random Forest classifiers in the context of IMDB movie reviews. This quiz covers key concepts, model evaluation, and data handling techniques essential for achieving accurate predictions. Perfect for students and enthusiasts of data science and natural language processing.