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canvaslatextikzr-exams

Is there a way to use LaTeX packages in the exams2canvas of R/exams?

I'm trying to setup up an exam using R/exams, using the function exams2canvas(). My questions contain LaTeX code that requires to use some packages (in particular tikz and tikz-qtree and a few other tikz libraries) but I cannot figure out how to import them.

To create a pdf, I manually modified the tex template (plain.tex) in the exams package of R, by adding the following two lines:

\usepackage{tikz}
\usepackage{tikz-qtree}

Could I perhaps modify the canvas file in a similar way? Is there another way that I can use LaTeX packages in exams2canvas()?

Minimal example:

\begin{question}
\Tree[.S [.NP [.D the ] [.N children ] ] [.VP [.V study ] ]  [.NP [.N books ] ]  ]
\begin{answerlist}
  \item 0.7
  \item 0.2
  \item 0.1
\end{answerlist}
\end{question}

\begin{solution}
\begin{answerlist}
  \item False
  \item False
  \item True
\end{answerlist}
\end{solution}

\exname{Trees}
\extype{schoice}
\exsolution{001}
Solution

  • The problem is that for Canvas output, just like for other HTML-based formats, the LaTeX code needs to be converted to HTML. And the HTML converters we use (tth and pandoc) both just support a limited number of LaTeX commands beyond the base LaTeX distribution.

    Thus, you need to compile tikz graphics in LaTeX and then convert them to a graphics format supported by HTML, e.g., SVG vector graphics or alternatively raster graphics such as PNG or JPG. This functionality is offered by the include_tikz() function in R/exams.

    I have modified your exercise so that the tikz code is only included as LaTeX for exams2pdf() and exams2nops() - which then need to be adapted to load tikz and tikz-qtree. Otherwise, the tikz code is rendered to SVG for which magick plus pdf2svg is used. Alternatively, you could also render to PNG, for example.

    So you can do:

    exams2html("tikz_tree.Rnw")

    or

    exams2nops("tikz_tree.Rnw", usepackage = c("tikz", "tikz-qtree"))

    etc.

    exams2canvas() will work like exams2html(). The modified tikz_tree.Rnw file is included at the end of the post. Some further pointers and details (including an R/Markdown version of the exercise) are available in this discussion in the R/exams forum on R-Forge: https://R-Forge.R-project.org/forum/forum.php?thread_id=33909&forum_id=4377&group_id=1337

    Some similar but more elaborate exercise templates are available on the R/exams web page:
    http://www.R-exams.org/templates/automaton/
    http://www.R-exams.org/templates/logic/

    tikz_tree.Rnw

    <<echo=FALSE, results=hide>>=
## determine the output type depending on exams2xyz interface:
## - plain .tex for exams2pdf, exams2nops which then need to use packages tikz and tikz-qtree
## - .svg for other HTML-based interfaces
typ <- if(match_exams_call() %in% c("exams2pdf", "exams2nops")) "tex" else "svg"

## TikZ code (note that backslashes need to be escaped"
tikz_tree <- "\\Tree[.S [.NP [.D the ] [.N children ] ] [.VP [.V study ] ]  [.NP [.N books ] ]  ]"
@

\begin{question}

<<echo=FALSE, results=tex>>=
include_tikz(tikz_tree, name = "tik_tree", format = typ,
  packages = "tikz-qtree", width = "5cm")
@

\begin{answerlist}
  \item 0.4
  \item 0.2
  \item 0.9
\end{answerlist}
\end{question}

\begin{solution}
\begin{answerlist}
  \item False
  \item False
  \item True
\end{answerlist}
\end{solution}

\exname{Tree}
\extype{schoice}
\exsolution{001}