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: "To add tool tips to our heat map, the HeatModSVG program will prompt us for a data file in addition to the SVG file that we want to modify."

A block of code is set as follows:

if (!require("gplots")) {
install.packages("gplots", dependencies = TRUE)
library(gplots)
}
if (!require("MASS")) {
install.packages("MASS", dependencies = TRUE)
library(MASS)
}

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

-- "t" for tab
-- "c" for comma
: c
Column names? (y/n): y
Row names? (y/n): n

Read in data from car_data.csv:

Any command-line input or output is written as follows:

update.packages("gplots")
update.packages("lattice")

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: "First, the program asks us whether we want to add Tool Tips or Zoom and Panning or both."