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 K-nearest neighbors to find outliers

Machine learning tools can help us identify observations that are unlike others when we have unlabeled data – that is, when there is no target or dependent variable. Even when selecting targets and features is relatively straightforward, it might be helpful to identify outliers without making any assumptions about relationships between features, or the distribution of features.

Although we typically use K-nearest neighbors (KNN) with labeled data, for classification or regression problems, we can use it to identify anomalous observations. These are observations where there is the greatest difference between their values and their nearest neighbors' values. KNN is a very popular algorithm because it is intuitive, makes few assumptions about the structure of the data, and is quite flexible. The main disadvantage of KNN is that it is not as efficient as many other approaches, particularly parametric techniques such as linear regression...