R All-in-One For Dummies

Chapter 9

In Due Time

IN THIS CHAPTER

Understanding time series

Moving averages

Smoothing things out

In many fields (science, medicine, business), it’s often necessary to take measurements over successive intervals of time. When you have this kind of data, you have yourself a time series. This chapter tells you about time series and how to use R to analyze them and use them to make forecasts.

A Time Series and Its Components

Managers often base their decisions on time series — like sales figures — and the numbers in a time series typically show numerous ups and downs.

Let’s look at an example. The (totally fictional) FarDrate Timepiece Corporation markets the beautifully designed MeesKyte watch, and they gather the quarterly national sales figures. Table 9-1 shows these quarterly sales figures from 2016–2020.

TABLE 9-1 Quarterly Sales Figures for the MeesKyte watch

Year	Quarter	Sales X 100,000
2016	1	57
	2	84
	3	68
	4	100
2017	1	63
	2	81
	3	73
	4	110
2018	1	70
	2	87
	3	75
	4	112
2019	1	78
	2	95
	3	88
	4	116
2020	1	82
	2	99
	3	92
	4	122

To work with R’s time series capabilities, we first put the numbers in the proper format. We begin by creating a vector of the numbers in the ...