To cite package 'sparktex' in publications use:

Thomas J. Leeper (2013). sparktex: Generate LaTeX sparklines. R package version 0.1.

Corresponding BibTeX entry:

  @Manual{,
    title = {sparktex: Generate LaTeX sparklines},
    author = {Thomas J. Leeper},
    year = {2013},
    note = {R package version 0.1},
  }