title: How can I plot a zoomable plot in knitr
body: <p>I an using <code>knitr</code> for automatic html reports. I would like to be able to plot simple scatter plots (like time serie plots) but interactive ones, that would be zoomable.
  Ideally I could then use it in a <code>knitr</code> html document.
  I had a look at <code>rgl</code> but it seems overkill for my simple needs. What should I use ?</p>