Sweave 文档中 R 注释中对图形的动态引用

Question

我想找到一种使用 LaTeX \ref{} 标记在 Sweave .Rnw 文件中的 R 代码中进行注释的方法。这里有两个例子，一个是印刷版的

http:// /cm.bell-labs.com/cm/ms/departments/sia/project/nlme/UGuide.pdf

和一个用于使用的文件：

.Rnw 文件

% File: example.Rnw

\documentclass{article}
\usepackage{fullpage}
\usepackage{graphics}
\usepackage{Sweave} 
\usepackage[margin = 10pt, font=small, labelfont={bf}]{caption}

\begin{document}

Here is an example file to show what I want to do.  I would like to figure out how to use the \LaTeX\ reference command to reference a figure being generated by R code.  Note in the R code, in a comment there is a reference to the figure, but of course the output file shows a verbatim copy of the \LaTeX\ markup.  Does anyone know how to get something for Figure \ref{fig2}?

<< example plot >>=
library(reshape)
library(ggplot2)

n <- 100
lambda <- 1 / 3 
x <- seq(0, qexp(0.999, rate = lambda), length = n)
q1.a <- data.frame(x =   x,
                   f =   dexp(x, rate = lambda),
                   F =   pexp(x, rate = lambda))

q1.a <- melt(q1.a, id.vars = 'x')
g <- ggplot(q1.a) +                                     # Produces \ref{fig1} 
       aes(x = x, y = value) + 
       geom_line() + 
       facet_wrap( ~ variable, scale = "free_y")
ggsave(g, filename = "example1.jpeg")                    
@

\begin{figure}[h]
\centering
\includegraphics[width = 0.48\textwidth]{./example1}
\caption{Exponential Distribution based plots.}
\label{fig1}
\end{figure}

Here is more of what I would like to see:

<< example plot 2 >>=
ggsave(g + geom_point(), filename = "example2.jpeg")    # Produces Figure 2
@

\begin{figure}
\centering
\includegraphics[width = 0.48\textwidth]{./example2}
\caption{Exponential Distribution based plots with points and lines.}
\label{fig2}
\end{figure}

\end{document}

和 pdf 是使用 R 命令构建

Sweave(file = 'example.Rnw',
       engine = "R",
       keep.source = 'TRUE',
       echo = 'TRUE',
       results = 'verbatim')

tools::texi2dvi(file  = "example.tex",
                pdf   = TRUE,
                clean = TRUE)

的洞察如何这样做就太好了。

Answer 1

解决此问题的一种方法是重新定义 Sinput 环境，其中源代码由 Sweave 包装。默认情况下，它是一个简单的逐字环境，不由 latex 处理令牌。诀窍是重新定义它以使用 alltt 环境，该环境允许在 alltt 环境内解析某些标记。请注意，这可能会导致我不知道的不良副作用，因此请谨慎使用！

这是一个有效的可重现示例。如果编译它，您将生成一个文件，其中 ref{fig1} 被图形编号替换。

\documentclass{article}
\usepackage{Sweave}
\usepackage{alltt}
\renewenvironment{Sinput}{\begin{alltt}}{\end{alltt}}

\begin{document}

In this document, we will create a plot using `R`, and reference its position in 
the source code.

<<produce-plot, results = hide>>=
pdf('example1.pdf')
plot(1:10, 1:10)     # Produces Figure \ref{fig1}
dev.off()
@

\begin{figure}
\includegraphics{example1.pdf}
\caption{Figure 1}
\label{fig1}
\end{figure}

\end{document}