Text Classification Application

By Bill Sharlow

Day 7: DIY Natural Language Processing Applications

Welcome back to our NLP journey! Today, we’re exploring text classification, an essential application of natural language processing that involves categorizing text documents into predefined classes or categories based on their content. Text classification finds applications in spam detection, sentiment analysis, topic categorization, and more. In this post, we’ll dive into the concepts behind text classification, discuss its applications, and build a simple text classification application using Python libraries like NLTK and spaCy.

Understanding Text Classification

Text classification, also known as document classification or text categorization, is the process of assigning one or more predefined labels or categories to text documents based on their content. It involves training machine learning models on labeled training data to learn patterns and relationships between the features (words, phrases, etc.) and the corresponding labels. Text classification tasks can be binary (two classes) or multiclass (multiple classes).

Applications of Text Classification

Text classification has numerous applications across various domains, including:

  1. Spam Detection: Classifying emails or messages as spam or non-spam based on their content.
  2. Sentiment Analysis: Categorizing text documents as positive, negative, or neutral based on the sentiment expressed.
  3. Topic Categorization: Assigning topics or categories to news articles, blog posts, or social media posts.
  4. Intent Detection: Identifying the intent or purpose behind user queries in chatbots or virtual assistants.

Building a Simple Text Classification Application with NLTK

Let’s create a basic text classification application using NLTK’s Naive Bayes classifier. In this example, we’ll classify text documents into two categories: positive and negative.

import nltk
from nltk.corpus import movie_reviews
import random

# Prepare the dataset
documents = [(list(movie_reviews.words(fileid)), category)
             for category in movie_reviews.categories()
             for fileid in movie_reviews.fileids(category)]

# Define features
all_words = nltk.FreqDist(w.lower() for w in movie_reviews.words())
word_features = list(all_words)[:2000]

def document_features(document):
    document_words = set(document)
    features = {}
    for word in word_features:
        features[word] = (word in document_words)
    return features

# Create feature sets
featuresets = [(document_features(d), c) for (d,c) in documents]
train_set, test_set = featuresets[:1600], featuresets[1600:]

# Train the classifier
classifier = nltk.NaiveBayesClassifier.train(train_set)

# Evaluate the classifier
accuracy = nltk.classify.accuracy(classifier, test_set)
print(f"Accuracy: {accuracy}")

Building a Simple Text Classification Application with spaCy

Now, let’s explore text classification using spaCy, a library known for its advanced NLP capabilities.

import spacy

def classify_text(text):
    nlp = spacy.load('en_core_web_sm')
    doc = nlp(text)
    return doc.cats

# Example usage
sample_text = "This movie was fantastic!"
classification_result = classify_text(sample_text)


In today’s post, we’ve explored the concept of text classification and its significance in categorizing text documents based on their content. We’ve built a simple text classification application using both NLTK and spaCy, demonstrating their capabilities in classifying text into predefined categories.

In the next post, we’ll delve into topic modeling, another intriguing application of NLP that involves discovering latent topics within a collection of text documents. Stay tuned for more hands-on examples and insights as we continue our NLP journey!

If you have any questions or thoughts on text classification, feel free to share them in the comments section below. Happy classifying, and see you in the next post!

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