Visualize data

Plotting your data is one of the quickest and easiest ways to spot oddities. Whenever you import a new data set, one of the first things you should do is plot the variables to ensure they are reasonable.

In this exercise, you will use the plot() function to visualize some AAPL data from Yahoo Finance. A stock split in June 2014 caused a huge price change. A stock split is when a company simultaneously increases the number of shares outstanding and decreases the stock price, so that the value of the company remains unchanged. For example, a 2-for-1 stock split would give investors 2 shares for every 1 share they own, but reduce the stock price by 1/2 at the same time.

You will also get some more practice using the quantmod extractor functions, Cl() and Ad() to access the data in the close and adjusted close columns, respectively. Yahoo Finance provides the adjusted close column, which is a split- and dividend-adjusted version of the close prices. Ad() simply extracts the adjusted close column. You will learn more about the adjustment process in the next chapter.

Instructions

AAPL is available in your workspace - consisting of Apple stock data (imported from Yahoo Finance) from January 2007 through September 15, 2017.

Look at the tail() of AAPL.
Plot the AAPL close price.
Plot the AAPL adjusted close price.

Take Hint (-30xp)