 for manual tours by manipulating the contribution of 
  a single variable at a time Cook &amp; Buja (1997) 
  &lt;doi:10.1080/10618600.1997.10474754&gt;. Other types of tours, such as grand 
  (random walk) and guided (optimizing some objective function) are available 
  in the tourr package Wickham et al. &lt;doi:10.18637/jss.v040.i02&gt;. 
  spinifex builds on tourr and can render tours with gganimate and 
  plotly graphics, and allows for exporting as an .html widget and as an .gif, 
  respectively. Thi