texPreview comes with LaTeX packages built in for each render, but the user can add any TeX library that they have installed on the machine using build_usepackage. This object can then be used in the usrPackages parameter in tex_preview.

Usage

usepackage

build_usepackage(pkg = 'xcolor')
## [1] "\\usepackage{xcolor}"

usepackage with options

build_usepackage(pkg = 'xcolor',options = 'usenames')
## [1] "\\usepackage[usenames]{xcolor}"

vectorized usepackage

geom.opts=c('paperwidth=35cm','paperheight=35cm','left=2.5cm','top=2.5cm')
use.opts="\\usetikzlibrary{mindmap,backgrounds}"

m <- mapply(
  FUN        = build_usepackage,
  pkg        = list('times','geometry','tikz'),
  options    = list(NULL   ,geom.opts ,NULL),
  uselibrary = list(NULL   ,NULL      ,use.opts)
)

unlist(m)
## [1] "\\usepackage{times}"                                                          
## [2] "\\usepackage[paperwidth=35cm,paperheight=35cm,left=2.5cm,top=2.5cm]{geometry}"
## [3] "\\usepackage{tikz}"                                                           
## [4] "\\usetikzlibrary{mindmap,backgrounds}"