Using ggvis in Rnw with knitr - r

Question

I wonder if I can use ggvis in .Rnw with knitr. I tried the following code in RStudio Version 0.98.1091. But it is not working.
\documentclass{book}
\usepackage[T1]{fontenc}
\usepackage{float}
\usepackage{booktabs}
\usepackage{dcolumn}
\usepackage{geometry}
\geometry{verbose,tmargin=2cm,bmargin=2cm,lmargin=2cm,rmargin=2cm}
\begin{document}
\chapter{Test}
\begin{figure}[H]
<< label = Plot1, fig.lp = "Plot1", fig.cap = "Test Plot" >>=
library(ggvis)
p <- mtcars %>% ggvis(x = ~wt, y = ~mpg) %>% layer_points()
print(p) # Commenting this line will compile the document
#
\end{figure}
\end{document}
It throws the following error:
LaTeX errors:
! Missing $ inserted.
<inserted text>
$
l.70 \end{kframe}<!--html_
preserve--><div id="plot_id298740869-container" cl...
! Please use \mathaccent for accents in math mode.
Edited
Commenting the line print(p) will compile the document without any error.
Would be sufficient if there is a command like ggsave() to save the ggvis plots.

Answer 1

Yes.
The export_png function can create a PNG image from a ggvis object.
It uses the node javascript interpreter, and node needs the vega package installed.
At the linux command line, I can do this with:
sudo npm -g install vega
to install the vega package globally using the node package manager. I don't know how you do this on a Windows or Mac box.
Once that's done, you can:
\documentclass{book}
\usepackage[T1]{fontenc}
\usepackage{float}
\usepackage{booktabs}
\usepackage{dcolumn}
\usepackage{geometry}
\geometry{verbose,tmargin=2cm,bmargin=2cm,lmargin=2cm,rmargin=2cm}
\begin{document}
\chapter{Test}
\begin{figure}[H]
<< label = Plot1, fig.lp = "Plot1", fig.cap = "Test Plot" >>=
library(ggvis)
p <- mtcars %>% ggvis(x = ~wt, y = ~mpg) %>% layer_points()
export_png(p,"Plot1.png")
#
\includegraphics[width=0.8\textwidth]{Plot1.png}
\end{figure}
\end{document}
do: knit2pdf("gg.Rnw")
and get:
Note you'll have to add captions and labels manually. Perhaps Yihui can be persuaded to integrate this better into knitr, or there may be a way using some of the knitr hooks. Anyway, concept proved...