Conventions

In this book, you will find a number of styles of text that distinguish between 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: "We have used the png() function to save the plot as a PNG."

Any command line code is written as:

k = matrix((1:4),2,2)
l = matrix((5:10),2,3)
dim(k)
dim(l)

In R it is a general practice to use <- for assignment instead of the = sign. In all the recipes, I have followed the = sign for assignment. You should note that if you refer to blogs or websites related to R, you may encounter the <- sign in the code files.

New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "In order to write a simple function in R, we must first open a new R script by navigating to File | New file."