Book Image

Time Series Indexing

By : Mihalis Tsoukalos
Book Image

Time Series Indexing

By: Mihalis Tsoukalos

Overview of this book

Time series are everywhere, ranging from financial data and system metrics to weather stations and medical records. Being able to access, search, and compare time series data quickly is essential, and this comprehensive guide enables you to do just that by helping you explore SAX representation and the most effective time series index, iSAX. The book begins by teaching you about the implementation of SAX representation in Python as well as the iSAX index, along with the required theory sourced from academic research papers. The chapters are filled with figures and plots to help you follow the presented topics and understand key concepts easily. But what makes this book really great is that it contains the right amount of knowledge about time series indexing using the right amount of theory and practice so that you can work with time series and develop time series indexes successfully. Additionally, the presented code can be easily ported to any other modern programming language, such as Swift, Java, C, C++, Ruby, Kotlin, Go, Rust, and JavaScript. By the end of this book, you'll have learned how to harness the power of iSAX and SAX representation to efficiently index and analyze time series data and will be equipped to develop your own time series indexes and effectively work with time series data.
Table of Contents (11 chapters)

Understanding MPdist

Now that we know about the Matrix Profile, we are ready to learn about MPdist and how the Matrix Profile is used in the calculation of MPdist. The paper that defines the MPdist distance is Matrix Profile XII: MPdist: A Novel Time Series Distance Measure to Allow Data Mining in More Challenging Scenarios, written by S. Gharghabi, S. Imani, A. Bagnall, A. Darvishzadeh, and E. Keogh (https://ieeexplore.ieee.org/abstract/document/8594928).

The intuition behind MPdist is that two time series can be considered similar if they have similar patterns throughout their duration. Such patterns are extracted in the form of subsequences using a sliding window. This is illustrated in Figure 7.2:

Figure 7.2 – Grouping time series

Figure 7.2 – Grouping time series

In Figure 7.2, we see that MPdist (c) understands the similarity between time series that follow the same pattern better, whereas Euclidean distance (b) compares time series based on time, and therefore groups the...