While R's base graphics library is almost limitlessly flexible when it comes to create static graphics and data visualizations, new Web-based technologies like d3 and webgl open up new horizons in high-resolution, rescalable and interactive charts. Graphics built with these libraries can easily be embedded in a webpage, can be dynamically resized while maintaining readable fonts and clear lines, and can include interactive features like hover-over data tips or movable components. And thanks to htmlwidgets for R, you can easily create a variety of such charts using R data and functions, explore them in an interactive R session, and include them in Web-based applications for others to experience.
This htmlwidgets showcase allows you to try out a few such charts, but to see the full diversity of charts available check out the new htmlwidgets gallery. It's an index of packages on CRAN and on Github that create htmlwidgets visualizations. (Be sure to turn OFF the "CRAN Only" switch in the top-right corner to see the full range available.)
There's a huge range of charts to explore, including scrollable geographic maps, heat maps, word clouds, streamgraphs, bubble charts and much much more. There are also general interfaces to interactive graphics systems like Plotly and Bokeh. Browse around the gallery to find a chart of interest, click to find the associated R package, install it, and get visualizing!
By the way, while interactive charts are great for hands-on applications, they're not necessarily so helpful for printed reports or presentations. If you're looking for R graphics of the static variety, check out the R Graph Gallery. But if interactive and Web-enabled is your thing, check out the link below.
htmlwidgets for R: Gallery