Sentiment Analysis Techniques (Lexicon-based, Machine Learning)

Sentiment analysis, also known as opinion mining, is a popular branch of Natural Language Processing (NLP) that involves determining the sentiment or emotion behind a piece of text. This analysis allows us to classify text as positive, negative, or neutral, providing valuable insights into customer opinions, social media sentiment, and public perception.

In this article, we will explore two common approaches for sentiment analysis: lexicon-based techniques and machine learning algorithms.

Lexicon-based Techniques

Lexicon-based techniques employ pre-defined sentiment lexicons or dictionaries to assign sentiment scores to words or phrases in a given text. These lexicons contain entries with associated sentiment polarities, usually represented by numerical values. Some popular lexicons used in sentiment analysis are the SentiWordNet, AFINN, and VADER lexicons.

The basic idea behind lexicon-based techniques is to calculate an aggregate sentiment score for a text by summing up the sentiment scores of individual words or phrases. The resulting sentiment score can be used to classify the text as positive, negative, or neutral.

One of the simplest lexicon-based techniques is the bag of words approach. This technique involves creating a set of positive and negative words from the lexicon and counting the occurrences of these words in the text. By comparing the positive and negative word counts, we can determine the sentiment of the text.

Lexicon-based techniques are relatively easy to implement and computationally efficient. However, they may not perform well with complex linguistic structures, sarcasm, or domain-specific sentiments. Therefore, they are often used as a baseline or in combination with other approaches.

Machine Learning Algorithms

Machine learning algorithms have gained popularity in sentiment analysis due to their ability to learn from data and automatically discover patterns and features indicating sentiment. These algorithms typically require a labeled dataset, where each text is already assigned a sentiment label (positive, negative, or neutral).

One common approach in machine learning-based sentiment analysis is to use a supervised learning model such as Naive Bayes, Support Vector Machines (SVM), or Random Forests. These models are trained on the labeled dataset to learn the relationship between the features (e.g., words, phrases, n-grams) and the sentiment labels. Once trained, the model can predict the sentiment of new, unseen texts.

Another approach is deep learning, which utilizes neural networks to automatically learn representations of text data and perform sentiment classification. Models like Recurrent Neural Networks (RNNs), specifically Long Short-Term Memory (LSTM) networks, have shown excellent performance in sentiment analysis tasks. These models can capture long-range dependencies and sequential information in text, making them well-suited for sentiment analysis.

Machine learning algorithms for sentiment analysis generally require more computational resources and extensive labeled datasets for training. However, they can handle complex linguistic structures, capture intricate sentiment patterns, and perform well in a wide range of domains.


Sentiment analysis techniques, whether based on lexicons or machine learning algorithms, have revolutionized the way businesses gather insights from text data. Lexicon-based approaches are straightforward and computationally efficient, but may struggle with nuances and domain-specific sentiment. On the other hand, machine learning algorithms offer more sophisticated analysis by learning from labeled datasets and capturing intricate sentiment patterns.

Ultimately, the choice of sentiment analysis technique depends on the specific requirements and constraints of the task at hand. Both approaches have their strengths and weaknesses, and often it is beneficial to experiment with a combination of lexicon-based and machine learning techniques to achieve the most accurate and reliable sentiment analysis results.

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