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Learning R Programming

You're reading from  Learning R Programming

Product type Book
Published in Oct 2016
Publisher Packt
ISBN-13 9781785889776
Pages 582 pages
Edition 1st Edition
Languages
Author (1):
Kun Ren Kun Ren
Profile icon Kun Ren

Table of Contents (21) Chapters

Learning R Programming
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
1. Quick Start 2. Basic Objects 3. Managing Your Workspace 4. Basic Expressions 5. Working with Basic Objects 6. Working with Strings 7. Working with Data 8. Inside R 9. Metaprogramming 10. Object-Oriented Programming 11. Working with Databases 12. Data Manipulation 13. High-Performance Computing 14. Web Scraping 15. Boosting Productivity

Matrix


A matrix is a vector represented and accessible in two dimensions. Therefore, what applies to vectors is most likely to apply to a matrix. For example, each type of vector (for example, numeric vector or logical vectors) has its matrix version, that is, there are numeric matrices, logical matrices, and so on.

Creating a matrix

We can call matrix() to create a matrix from a vector by setting up one of its two dimensions:

matrix(c(1, 2, 3, 2, 3, 4, 3, 4, 5), ncol = 3)
##      [,1] [,2] [,3]
## [1,]   1    2    3
## [2,]   2    3    4
## [3,]   3    4    5

By specifying ncol = 3, we mean that the provided vector should be regarded as a matrix with 3 columns (and 3 rows automatically). You may feel the original vector is not as straightforward as its representation. To make the code more user-friendly, we can write the vector in multiple lines:

matrix(c(1, 2, 3,  4, 5, 6,  7, 8, 9), nrow = 3, byrow = FALSE)
##     [,1] [,2] [,3]
## [1,]  1    4    7
## [2,]  2    5    8
## [3,] ...
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