[R] Centering graphics by default in Sweave

[Frank E Harrell Jr]

Thanks very much Marc for the very useful ideas.

I do hope there will be an even more concise way to do this.  At present 
I'm not using figure environments in Sweave as in stat reports I don't 
usually need floats.

I tried re-defining \includegraphics to include \centerline but got into 
infinite recursion as expected.  It would be nice if LaTeX had an easy 
way to \renewcommand that allowed use of the existing definition of the 
command.

Frank


Marc Schwartz wrote:
> 
> On Jun 14, 2009, at 2:28 PM, Frank E Harrell Jr wrote:
> 
>> Is there an elegant way to get Sweave to center graphics by default? 
>> I'd like to use \centerline{\includegraphics{}} etc. to save some 
>> vertical space that \begin{center} ... \end{center} uses, and I'd like 
>> to avoid centering with each <<fig=T>>=
> 
> Frank,
> 
> My comments below are based upon the presumption that you are using a 
> 'figure' environment for your plots.
> 
> As far as I know, there is no Sweave option for this, however, reviewing 
> the code for the handling of the 'include' option, it looks like (at 
> first glance) that it might not be too difficult to add one. The 
> 'includegraphics' statement is output as part of the handling of the 
> 'include' option code. It would take more time to be sure that I am not 
> missing something.
> 
> However, there is an alternative, which is to define a new environment 
> using the \newenvironment command and have it encapsulate the normal 
> 'figure' environment along with a \centering command. \centering will 
> accomplish the same thing as using \centerline, which is to save some 
> vertical space after the figure environment if otherwise using the 
> 'center' environment. BTW, this extra vertical space occurs because the 
> 'center' environment is built on top of the 'list' environment, which 
> introduces different paragraph spacing.
> 
> To that end, below is some example .Rnw code for a document including 
> the specification of a new environment called 'centerfig', which can 
> then be used in the same way you would call the regular 'figure' 
> environment. The definition consists of two lines. The first is what is 
> used at the beginning of the environment and the second is used at the 
> end. In this case, the first line calls the figure environment with the 
> addition of \centering. The second line simply ends the figure 
> environment. Think of the two lines as macro substitutions.
> 
> I have included a copy of a PDF file that contains the result of this 
> code. Note that the first and third pages are essentially the same, 
> while the second has extra space after the figure when 
> \begin{center}...\end{center} is used.
> 
> This would be one way of altering the default behavior of the figure 
> environment, so that it is centered by default. Now just use:
> 
>   \begin{centerfig}
>   ...
>   \end{centerfig}
> 
> instead of:
> 
>   \begin{figure}
>     \begin{center}
>     ...
>     \end{center}
>   \end{figure}
> 
> HTH,
> 
> Marc Schwartz
> 
> 
> 
> \documentclass[10pt]{article}
> \usepackage{graphicx}
> 
> \begin{document}
> 
> \setlength{\parindent}{0pt}
> \setlength{\parskip}{0pt}
> 
> 
> %% Here is the new environment called centerfig
> \newenvironment{centerfig}
> {\begin{figure}[htp]\centering}
> {\end{figure}}
> 
> 
> Here is some text before the figure
> 
> \begin{centerfig}
> <<fig=TRUE>>=
>   x <- seq(0, 5, 0.1)
>   y <- x^3
>   par(mar = c(2, 3, 0, 0))
>   plot(x, y, ann = FALSE, type = "l", las = 1)
> @
> \caption{Using ``centerfig''}
> \end{centerfig}
> 
> Here is some text after the figure
> 
> 
> \clearpage
> 
> 
> Here is some text before the figure
> 
> \begin{figure}[htp]
> \begin{center}
> <<fig=TRUE>>=
>   x <- seq(0, 5, 0.1)
>   y <- x^3
>   par(mar = c(2, 3, 0, 0))
>   plot(x, y, ann = FALSE, type = "l", las = 1)
> @
> \caption{Using ``figure'' with 
> $\backslash$begin\{center\}...$\backslash$end\{center\}}
> \end{center}
> \end{figure}
> 
> Here is some text after the figure
> 
> 
> \clearpage
> 
> 
> Here is some text before the figure
> 
> \begin{figure}[htp]
> \begin{Schunk}
> \begin{Sinput}
>  > x <- seq(0, 5, 0.1)
>  > y <- x^3
>  > par(mar = c(2, 3, 0, 0))
>  > plot(x, y, ann = FALSE, type = "l", las = 1)
> \end{Sinput}
> \end{Schunk}
> %% Use same graphic file as the first
> \centerline{\includegraphics{test-001}}
> \caption{Using ``figure'' with $\backslash$centerline}
> \end{figure}
> 
> Here is some text after the figure
> 
> 
> \end{document}
> 
> 
> 
> 
> 


-- 
Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University