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

Feature binning

Sometimes, we will want to convert a continuous feature into a categorical feature. The process of creating k equally spaced intervals from the minimum to the maximum value of a distribution is called binning or, the somewhat less-friendly term, discretization. Binning can address several important issues with a feature: skew, excessive kurtosis, and the presence of outliers.

Equal-width and equal-frequency binning

Binning might be a good choice with the COVID case data. Let's try that (this might also be useful with other variables in the dataset, including total deaths and population, but we will only work with total cases for now. total_cases is the target variable in the following code, so it is a column – the only column – on the y_train DataFrame):

  1. First, we need to import EqualFrequencyDiscretiser and EqualWidthDiscretiser from feature_engine. Additionally, we need to create training and testing DataFrames from the COVID data...