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

Using principal component analysis

A very different approach to feature selection than any of the methods we have discussed so far is PCA. PCA allows us to replace the existing feature set with a limited number of components, each of which explains an important amount of the variance. It does this by finding a component that captures the largest amount of variance, followed by a second component that captures the largest amount of remaining variance, and then a third component, and so on. One key advantage of this approach is that these components, known as principal components, are uncorrelated. We discuss PCA in detail in Chapter 15, Principal Component Analysis.

Although I include PCA here as a feature selection approach, it is probably better to think of it as a tool for dimension reduction. We use it for feature selection when we need to limit the number of dimensions without sacrificing too much explanatory power.

Let's work with the NLS data again and use PCA to...