對Sweave文檔中的R註釋中的數字的動態引用

Question

我想找到一種方法來使用LaTeX \ref{}標記在Sweave .Rnw文件中註釋R代碼。這裏有兩個例子，一個在打印

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

和一個使用與工作：

的.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是建立一個與R命令

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

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

任何有關這將是如何偉大的見識。

Answer 1

以下是通過重新定義源代碼被Sweave包裝的Sinput環境來解決此問題的一種方法。默認情況下，它是一個簡單的verbatim環境，不會由latex處理令牌。竅門是重新定義它以使用alltt環境，該環境允許在alltt環境中解析一些標記。請注意，這可能會導致我不知道的不需要的副作用，請謹慎使用！

這是一個可重複使用的例子。如果您編譯它，您將生成一個文件，其中ref{fig1}被圖號替換。

\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}