Before getting our hands dirty, let's conduct a brief data examination. The iris data set could be used from the beginning to the end of this chapter, as it displays simultaneously discrete (Species) and continuous variables (petal lengths/widths, sepal lengths/widths), but let's get some fresh air.
Data set Salaries coming from the car package shows information about nine-month salary for professors in a college in the U.S. between 2008 and 2009. It holds exactly the kind of data that we need. This recipe will look for car package among the already installed packages. If it's already installed, recipe proceeds to a quick data exploration, otherwise it installs car at the first place.
