In this book, you will find a number of styles of text that distinguish among different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "To compile the function, we will use the cmpfun() function in the compiler package."

A block of code is set as follows:

fibonacci_rec <- function(n) {
    if (n <= 1) {
        return(n)
    }
    return(fibonacci_rec(n - 1) + fibonacci_rec(n - 2))
}

New terms and important words are shown in bold. Words that you see on the screen, in menus or dialog boxes for example, appear in the text like this: "Be sure to select the Package authoring installation and Edit the system PATH options in the installation wizard."