To cite package ‘sparkline’ in publications use:

  Vaidyanathan R, Russell K, Watts G (2016). _sparkline: 'jQuery'
  Sparkline 'htmlwidget'_. R package version 2.0,
  <https://github.com/htmlwidgets/sparkline>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {sparkline: 'jQuery' Sparkline 'htmlwidget'},
    author = {Ramnath Vaidyanathan and Kent Russell and Gareth Watts},
    year = {2016},
    note = {R package version 2.0},
    url = {https://github.com/htmlwidgets/sparkline},
  }