In this book, you will find a number of text styles 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: "In R, the forecast package has an accuracy function that can be used to calculate forecasting accuracy."

A block of code is set as follows:

df1 = sqlContext.read 
. format("json")  data format is json
. option("samplingRatio", "0.01")  set sampling ratio as 1%
. load("/home/alex/data1,json")  specify data name and location

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

sqlContext <- sparkRSQL.init(sc)

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: "Users can click on Create new note, which is the first line under Notebook on the first left-hand side column."