The purpose of this chapter is to set the stage for the book and for the upcoming chapters. We first overview classical information-theoretic problems and solutions. We then discuss emerging applications of information-theoretic methods in various data-science problems and, where applicable, refer the reader to related chapters in the book. Throughout this chapter, we highlight the perspectives, tools, and methods that play important roles in classic information-theoretic paradigms and in emerging areas of data science. Table 1.1 provides a summary of the different topics covered in this chapter and highlights the different chapters that can be read as a follow-up to these topics.

Dictionary learning has emerged as a powerful method for data-driven extraction of features from data. The initial focus was from an algorithmic perspective, but recently there has been increasing interest in the theoretical underpinnings. These rely on information-theoretic analytic tools and help us understand the fundamental limitations of dictionary-learning algorithms. We focus on theoretical aspects and summarize results on dictionary learning from vector- and tensor-valued data. Results are stated in terms of lower and upper bounds on sample complexity of dictionary learning, defined as the number of samples needed to identify or reconstruct the true dictionary underlying data from noiseless or noisy samples, respectively. Many analytic tools that help yield these results come from information theory, including restating the dictionary-learning problem as a channel-coding problem and connecting analysis of minimax risk in statistical estimation to Fano’s inequality. In addition to highlighting effects of parameters on the sample complexity of dictionary learning, we show the potential advantages of dictionary learning from tensor data and present unaddressed problems.