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

Summary

In this chapter, we looked at some common techniques for exploring data. We learned how to retrieve subsets of data when that is required for our analysis. We also used pandas methods to generate key statistics on features such as mean, interquartile range, and skew. This gave us a better sense of the central tendency, spread, and shape of the distribution of each feature. It also put us in a better position to identify outliers. Finally, we used the Matplotlib and Seaborn libraries to create histograms, boxplots, and violin plots. This yielded additional insights about the distribution of features, such as the length of the tail and divergence from the normal distribution.

Visualizations are a great supplement to the tools for univariate analysis that we have discussed in this chapter. Histograms, boxplots, and violin plots display the shape and spread of each feature's distribution. Graphically, they show what we may miss by examining a few summary statistics, such as where there is a bulge (or bulges) in the distribution and where the extreme values are. These visualizations will be every bit as helpful when we explore bivariate and multivariate relationships, which we will do in Chapter 2, Examining Bivariate and Multivariate Relationships between Features and Targets.