The gvisAreaChart function reads a data.frame and
creates text output referring to the Google Visualisation API, which can be
included into a web page, or as a stand-alone page.
The area chart is rendered within the browser using SVG or VML and
displays tips when hovering over points.
name of the character column which contains the category labels for
the x-axes.
yvar
a vector of column names of the numerical variables to be
plotted. Each column is displayed as a separate line.
options
list of configuration options for Google Area Chart.
[object Object]
Further possible components are, taken from
https://google-developers.appspot.com/chart/interactive/docs/gallery/areachart.html#Configuration_Options:
[obj