The Big R-Book

♣3♣Conventions

This book is formatted with LATEX. The people who know this markup language will have high expectations for the consistency and format of this book. As you can expect there is

1. a table of contents at the start;
2. an index at the end, from page 1103;
3. a bibliography on page 1088;
4. as well as a list of all short-hands and symbols used on page 1117.

This is a book with a programming language as leitmotif and hence you might expect to find a lot of chunks of code. R is an interpreted language and it is usually accessed by opening the software R (simply type R on the command prompt and press enter).¹

# This is code 
1+pi 
## [1] 4.141593 
Sys.getenv(c("EDITOR","USER","SHELL", "LC_NUMERIC")) 
##         EDITOR    USER    SHELL        LC_NUMERIC 
##          "vi"     "root"  "/bin/bash" "pl_PL.UTF-8" 

As you can see, the code is highlighted, that means that not all things have the same colour and it is easier to read and understand what is going on. The first line is a “comment” that means that R will not do anything with it, it is for human use only. The next line is a simple sum. In your R terminal, this what you will type or copy after the > prompt. It will rather look like this:

> # This is code 
> 1+pi 
[1] 4.141593 
> Sys.getenv(c("EDITOR","USER","SHELL","XDG_SESSION_TYPE") 
     EDITOR   USER         SHELL       LC_NUMERIC 
       "vi"   "philippe"  "/bin/bash" "pl_PL.UTF-8" 
> 

In this, book there is nothing in front of a command and the reply of R is preceded by two pound signs: “##.”² The pound sign (#) is also the symbol used ...