Visual Text Exploration as Part of Preprocessing Before Classification

Introduction

The process of text classification is a common task in natural language processing and machine learning. In order to classify text data, it's essential to preprocess the data first. One of the key aspects of preprocessing is to explore the data in order to understand its characteristics, identify patterns and outliers, and determine which techniques and methods should be used to clean and prepare the data for classification.

Visual text exploration is a powerful tool that can be used to gain insights and understanding of text data. By visualizing the data in different ways, it's possible to detect patterns and identify trends that might not be immediately apparent from just reading through the data. Additionally, visual text exploration can also bring ideas for processing actions that need to be taken on the dataset.

In this blog post, we will analyze modern tools that can be used for visual exploration of text data and provide generic ideas for textual data inspection that can be applied in many text-exploration tasks. We will cover techniques such as wordcloud, Sentiment Analysis and topic modeling which are widely used by researchers to analyze text data and extract insights. Additionally, we will also cover textual data cleaning and it's role in preprocessing of text data.

Textual data cleaning

Textual data cleaning is an essential step in the preprocessing of text data before classification. The goal of data cleaning is to prepare the data so that it can be easily understood and analyzed by machine learning algorithms.

There are multiple techniques such as:

• removing stop-words
• stemming and lematization
• Regular expressions to clean text data by removing special characters and unwanted elements, such as URLs or email addresses.
• Text normalization - converting all the text to lowercase, removing punctuation and converting numbers to words.

Textual data cleaning will be not discussed in details in this article.

Textual Data Exploration with Sentiment Analysis

Sentiment analysis is a method of determining the emotional tone of a piece of text, which can be useful for identifying patterns in text data. Sentiment analysis can be used to classify text as positive, negative, or neutral based on the words and phrases used in the text.

The process of sentiment analysis typically involves analyzing a piece of text and determining the presence and strength of various sentiment-bearing words or phrases. The text is then classified as having a positive, negative or neutral sentiment.

Sentiment analysis can be applied in a wide range of applications, such as customer feedback analysis, social media monitoring, and opinion mining. The output of sentiment analysis can help in identifying patterns in the data such as customer preferences, brand reputation and product feedback.

There are a variety of libraries and packages available for performing sentiment analysis. Some of the popular libraries are NLTK, TextBlob, VaderSentiment, and Pattern. Each library has its own unique features, such as NLTK has a comprehensive list of common english words to remove and TextBlob has a built in sentiment analysis function.

For example, using NLTK library, you can perform sentiment analysis using the VaderSentimentIntensityAnalyzer by creating an object of it and passing your text to the polarity_scores method, which returns a dictionary containing scores for each sentiment-negative, neutral and positive. With TextBlob, you can directly use the sentiment method, which returns a named tuple of form (polarity, subjectivity ) where polarity is a float within the range [-1.0, 1.0] and subjectivity is a float within the range [0.0, 1.0].

It is important to note that sentiment analysis is a complex task and the results can be affected by the language and context of the text. However, with the right tools and techniques, sentiment analysis can be a powerful way to gain insights and identify patterns in text data.

Textual Data Exploration with topic modeling

Topic modeling is a method of identifying the main topics or themes present in a large collection of text data. It can be used to uncover the hidden structure in the data and to understand the main concepts or ideas that are being discussed. Topic modeling can be used to classify text into predefined topics or to discover new and previously unknown topics.

The most common technique used in topic modeling is Latent Dirichlet Allocation (LDA). LDA is a probabilistic model that aims to uncover the underlying topics present in a corpus of text data by assuming that each document is a mixture of a small number of latent topics. It is a generative model that describes how a set of observations is generated by a set of latent variables.

There are many libraries and packages available that can be used to perform topic modeling, some of the most popular ones are Gensim, Mallet and LDAvis.

For example, Gensim is a python library that provides an implementation of LDA. It allows to create a corpus of text data, create a bag of words and then generate a set of topics using the LDA model. Gensim also provides functionality to evaluate the quality of the generated topics and the ability to visualize the topics using pyLDAvis.

Mallet, which is a Java-based library, can also be used for topic modeling. It provides additional functionality for visualizing topics as well as tools for evaluating the quality of the generated topics.

LDAvis is a R package that provides interactive visualizations of LDA models. It can be used to extract insights from the model, explore the generated topics and get a sense of the overall structure of the data.

Topic modeling can be a powerful tool for uncovering the hidden structure in large collections of text data. It can be used to classify text into predefined topics or to discover new and previously unknown topics. With the right tools and techniques, topic modeling can be a powerful way to gain insights and identify patterns in text data.

Conclusion

Visual text exploration is a powerful tool that can be used to gain insights and understanding of text data as part of preprocessing before classification. We have seen how techniques such as wordcloud, Sentiment Analysis, topic modeling, and textual data cleaning can be used to explore text data and extract insights.

Visual text exploration allows us to detect patterns and identify trends that might not be immediately apparent from just reading through the data. Additionally, these techniques can also bring ideas for processing actions that need to be taken on the dataset.

It is important to note that the techniques discussed in this post are just a starting point and there are many other tools and techniques that can be used for visual text exploration. Furthermore, the best approach will depend on the specific dataset and problem you are working on.

I encourage readers to try out the tools and techniques covered in this post and to use them in their own text exploration projects. With the right tools and techniques, you can gain valuable insights and improve the performance of text classification models.

References and Additional Resources

Here are some references and additional resources that readers can use to learn more about visual text exploration and related topics:

1. "Text Mining and Analysis: Practical Methods, Examples, and Case Studies Using SAS" by Michael J. A. Berry and Gordon S. Linoff
2. "Python Text Processing with NLTK 2.0 Cookbook" by Jacob Perkins
3. "Topic Modeling with Gensim (Python)" by Shilpa Arora, https://www.analyticsvidhya.com/blog/2016/08/beginners-guide-to-topic-modeling-in-python/
4. "Topic Modeling with Mallet" by J. Stephen Downie, http://mallet.cs.umass.edu/topics.php
5. "Interactive topic model visualization" by Carson Sievert, https://cran.r-project.org/web/packages/LDAvis/vignettes/details.pdf
6. "NLTK Sentiment Analysis" by "Natural Language Processing with Python" by Steven Bird, Ewan Klein, and Edward Loper, http://www.nltk.org/howto/sentiment.html
7. "TextBlob: Simplified Text Processing" by Steven Loria, http://textblob.readthedocs.io/en/dev/

If you have any further questions or would like to learn more about visual text exploration, I recommend consulting these resources as they provide detailed information on various techniques and tools that can be used to explore text data.

Credits:

Header graphics from , User:Ragettho found on wikimedia

Any comments or suggestions? Let me know.

@article{Saf2022Visual,
    author  = {Krystian Safjan},
    title   = {Visual Text Exploration as Part of Preprocessing Before Classification},
    journal = {Krystian's Safjan Blog},
    year    = {2022},
}