We define x as a year between 2008 and 2013 and y as the total number of smartphones sold that year, in millions. The table shows values of x and corresponding y values.
Year
2008 2009 2010 2011 2012 2013
Number of
smartphones
in millions
ly)
3.7
173
424
90
125
153.2
Is y a function of x? Explain why or why not.