Book Image

Data Cleaning and Exploration with Machine Learning

By : Michael Walker
Book Image

Data Cleaning and Exploration with Machine Learning

By: Michael Walker

Overview of this book

Many individuals who know how to run machine learning algorithms do not have a good sense of the statistical assumptions they make and how to match the properties of the data to the algorithm for the best results. As you start with this book, models are carefully chosen to help you grasp the underlying data, including in-feature importance and correlation, and the distribution of features and targets. The first two parts of the book introduce you to techniques for preparing data for ML algorithms, without being bashful about using some ML techniques for data cleaning, including anomaly detection and feature selection. The book then helps you apply that knowledge to a wide variety of ML tasks. You’ll gain an understanding of popular supervised and unsupervised algorithms, how to prepare data for them, and how to evaluate them. Next, you’ll build models and understand the relationships in your data, as well as perform cleaning and exploration tasks with that data. You’ll make quick progress in studying the distribution of variables, identifying anomalies, and examining bivariate relationships, as you focus more on the accuracy of predictions in this book. By the end of this book, you’ll be able to deal with complex data problems using unsupervised ML algorithms like principal component analysis and k-means clustering.
Table of Contents (23 chapters)
1
Section 1 – Data Cleaning and Machine Learning Algorithms
5
Section 2 – Preprocessing, Feature Selection, and Sampling
9
Section 3 – Modeling Continuous Targets with Supervised Learning
13
Section 4 – Modeling Dichotomous and Multiclass Targets with Supervised Learning
19
Section 5 – Clustering and Dimensionality Reduction with Unsupervised Learning

Naïve Bayes for text classification

It is perhaps surprising that an algorithm based on calculating conditional probabilities could be useful for text classification. But this follows fairly straightforwardly with a key simplifying assumption. Let’s assume that our documents can be well represented by the counts of each word in the document, without regard for word order or grammar. This is known as a bag-of-words. The relationship that a bag-of-words has to a categorical target – say, spam/not spam or positive/negative – can be modeled successfully with multinomial naïve Bayes.  

We will work with text message data in this section. The dataset we will use contains labels for spam and not spam messages.

Note

This dataset on text messages can be downloaded by the public at https://www.kaggle.com/datasets/team-ai/spam-text-message-classification. It contains two columns: the text message and the spam or not spam (ham) label.

Let’...