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 classical linear regression

In this section, we will specify a fairly straightforward linear model. We will use it to predict the implied gasoline tax of a country based on several national economic and political measures. But before we specify our model, we need to do the pre-processing tasks we discussed in the first few chapters of this book.

Pre-processing the data for our regression model

We will use pipelines to pre-process our data in this chapter, and throughout the rest of this book. We need to impute values where they are missing, identify and handle outliers, and encode and scale our data. We also need to do this in a way that avoids data leakage and cleans the training data without peeking ahead to the testing data. As we saw in Chapter 6, Preparing for Model Evaluation, scikit-learn’s pipelines can help with these tasks.

The dataset we will use contains the implied gasoline tax for each country and some possible predictors, including national income...