David Smith sheds some light on the ggiraph project:
R’s ggplot2 package is a well-known tool for producing beautiful static data visualizations that you can include in a printed report. But what if you want to include a ggplot2 graphic on a webpage and provide the ability for the user to interact with the data? The ggiraph package by David Gohel (available for installation via CRAN). WIth ggiraph, you can take an existing ggplot2 bar chart, scatterplot, boxplot, map, or many other types of chart and add one or both of the following iteractions:
Display a tooltip of your choice (e.g. data values or labels) when the cursor hovers over sections of the chart
Perform an action (a javascript function you provide: jump to another page, for example) when the viewer clicks on an element of the chart
I like it.