Package citations and references

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In the book I refer to the first use of a package in the text with the package name in bold and
citation: **lattice** package [@R-lattice]; thereafter, I just use lattice.
All packages used in the book have their BibTeX references in bib/packages.bib, and the keys are all of the form R-pkgname.

I would prefer to have the package name appear in (a) a distinctive font, (b) in color if possible,
(c) be able to generate the citations as needed, (d) and automatically generate index entries.

I describe this in `test/package-citations.html, also rendered in PDF.

I have a first go at a function pkg() which I intend to use inline as, r pkg(package), and to generate the citations
using r pkg(package, cite=TRUE), which should also generate index entries in LaTeX. (This function, and one to colorize() text are defined in R/common.R, which is source()d in every chapter file.)

My attempts to change the font or color of the package name now fail. How can I fix this?

pkg <- function(package, cite=FALSE, color="brown") {
  pkgname <- if(is.null(color)) package else colorize(package, color)
  ref <- paste0("`", pkgname, "`")
  if (cite) ref <- paste0(ref, " [@R-", package, "]")
  if (knitr::is_latex_output()) {
    ref <- paste0(ref, "\\index{`",package, "`}\\index{package!`", package, "`}")
      }

  ref
}