Book Image

R Data Structures and Algorithms

By : PKS Prakash, Achyutuni Sri Krishna Rao
Book Image

R Data Structures and Algorithms

By: PKS Prakash, Achyutuni Sri Krishna Rao

Overview of this book

In this book, we cover not only classical data structures, but also functional data structures. We begin by answering the fundamental question: why data structures? We then move on to cover the relationship between data structures and algorithms, followed by an analysis and evaluation of algorithms. We introduce the fundamentals of data structures, such as lists, stacks, queues, and dictionaries, using real-world examples. We also cover topics such as indexing, sorting, and searching in depth. Later on, you will be exposed to advanced topics such as graph data structures, dynamic programming, and randomized algorithms. You will come to appreciate the intricacies of high performance and scalable programming using R. We also cover special R data structures such as vectors, data frames, and atomic vectors. With this easy-to-read book, you will be able to understand the power of linked lists, double linked lists, and circular linked lists. We will also explore the application of binary search and will go in depth into sorting algorithms such as bubble sort, selection sort, insertion sort, and merge sort.
Table of Contents (17 chapters)
R Data Structures and Algorithms
Credits
About the Authors
Acknowledgments
About the Reviewer
www.PacktPub.com
Preface

Self-organizing lists


So far, we have learned that the performance of search can be enhanced by sorting the vectors based on their key values prior to the search operations. However, there seems to be an another approach for sorting vectors, which is not based on key values but on the expected frequency of accessing the key values for comparison purposes. This kind of sorting based on expected frequency of access can sometimes be cheaper compared to sorting based on key values, thereby increasing the performance of search operations.

Consider a vector V sorted based on the frequency of access of key values, but not on the value of its elements. In other words, the elements with a higher probability (pi ) of getting compared with the search element S is placed first, followed by the element with the second highest probability, and so on. The search for element S is performed sequentially on all the sorted elements in the vector. Upon multiple search iterations, the expected number of comparisons...