General aspects

The qplot (quick plot) function is a basic high-level function of ggplot2. The general syntax that you should use with this function is the following:

qplot(x, y, data, color, shape, size, facets, geom, stat)

The definitions of the various components of this function are as follows:

• x and y: These represent the variables to plot (y is optional, with a default value of NULL).
• data: This defines the dataset containing the variables.
• color, shape and size: These are the aesthetic arguments that can be mapped on additional variables.
• facets: This defines the optional faceting of the plot based on one variable contained in the dataset.
• geom: This allows you to select the actual visualization of the data, which, basically, will define the plot that will be generated. The possible values are point, line, and boxplot, and we will see several different examples in the next pages.
• stat: This defines the statistics to be used for the data.

These arguments represent the most important options...