To cite package ‘sparkline’ in publications use:

Vaidyanathan R, Russell K, Watts G (2019). sparkline: 'jQuery' Sparkline 'htmlwidget'. R package version 2.0, https://github.com/htmlwidgets/sparkline.

Corresponding BibTeX entry:

  @Manual{,
    title = {sparkline: 'jQuery' Sparkline 'htmlwidget'},
    author = {Ramnath Vaidyanathan and Kent Russell and Gareth Watts},
    year = {2019},
    note = {R package version 2.0},
    url = {https://github.com/htmlwidgets/sparkline},
  }