knitr-如何对齐代码和并排打印 [英] knitr - How to align code and plot side by side

问题描述

是否有一种简单的方法(例如，通过块选项)来获取块的源代码及其并排生成的绘图，如

is there a simple way (e.g., via a chunk option) to get a chunk's source code and the plot it produces side by side, as on page 8 (among others) of this document?

我尝试使用out.width="0.5\\textwidth", fig.align='right'，它使图正确地仅占据页面的一半并向右对齐，但是源代码显示在其顶部，这是正常的行为. 我想把它放在图的左侧.

I tried using out.width="0.5\\textwidth", fig.align='right', which makes the plot correctly occupy only half the page and be aligned to the right, but the source code is displayed on top of it, which is the normal behaviour. I would like to have it on the left side of the plot.

谢谢

示例代码:

<<someplot, out.width="0.5\\textwidth", fig.align='right'>>=
plot(1:10)
@

推荐答案

好吧，这最终比我想象的要棘手.

Well, this ended up being trickier than I'd expected.

在LaTeX方面， adjustbox 包可让您掌控一切并排对齐的情况，如tex.stackexchange.com上在这个极好的答案中所展示的.因此，我的一般策略是使用LaTeX代码包装所指示的R块的格式化，整理，着色的输出，该代码包括:(1)将其放置在adjustbox环境中； (2)将块的图形输出包含在其右边的另一个adjustbox环境中.为此，我需要用在文档<<setup>>=块的(2)部分中定义的自定义钩子替换 knitr 的默认块输出钩子.

On the LaTeX side, the adjustbox package gives you great control over alignment of side-by-side boxes, as nicely demonstrated in this excellent answer over on tex.stackexchange.com. So my general strategy was to wrap the formatted, tidied, colorized output of the indicated R chunk with LaTeX code that: (1) places it inside of an adjustbox environment; and (2) includes the chunk's graphical output in another adjustbox environment just to its right. To accomplish that, I needed to replace knitr's default chunk output hook with a customized one, defined in section (2) of the document's <<setup>>= chunk.

Section (1)定义了一个块挂钩，可用于基于每个块临时设置R的任何全局选项(尤其是此处的options("width")). 在此处查看问题和答案只处理这种设置的一部分.

Section (1) of <<setup>>= defines a chunk hook that can be used to temporarily set any of R's global options (and in particular here, options("width")) on a per-chunk basis. See here for a question and answer that treat just that one piece of this setup.

最后，第(3)节定义了一个针织模板"，每当要生成一个并排的代码块和图形时，都需要设置几个选项的捆绑包.定义后，它允许用户只需在块标题中键入opts.label="codefig"即可触发所有必需的操作.

Finally, Section (3) defines a knitr "template", a bundle of several options that need to be set each time a side-by-side code-block and figure are to be produced. Once defined, it allows the user to trigger all of the required actions by simply typing opts.label="codefig" in a chunk's header.

\documentclass{article}

\usepackage{adjustbox}            %% to align tops of minipages
\usepackage[margin=1in]{geometry} %% a bit more text per line

\begin{document}

<<setup, include=FALSE, cache=FALSE>>=
## These two settings control text width in codefig vs. usual code blocks
partWidth <- 45
fullWidth <- 80
options(width = fullWidth)

##  (1) CHUNK HOOK FUNCTION
##   First, to set R's textual output width on a per-chunk basis, we
## need to define a hook function which temporarily resets global R's
## option() settings, just for the current chunk
knit_hooks$set(r.opts=local({
    ropts <- NA
    function(before, options, envir) {
        if (before) {
            ropts <<- options(options$r.opts)
        } else {
            options(ropts)
        }
    }
}))

## (2) OUTPUT HOOK FUNCTION

##   Define a custom output hook function. This function processes _all_
## evaluated chunks, but will return the same output as the usual one,
## UNLESS a 'codefig' argument appeared in the chunk's header.  In that
## case, wrap the usual textual output in LaTeX code placing it in a
## narrower adjustbox environment and setting the graphics that it
## produced in another box beside it.

defaultChunkHook <- environment(knit_hooks[["get"]])$defaults$chunk

codefigChunkHook <- function (x, options) {
        main <- defaultChunkHook(x, options)
        before <-
            "\\vspace{1em}\n
             \\adjustbox{valign=t}{\n
             \\begin{minipage}{.59\\linewidth}\n"
        after <-
            paste("\\end{minipage}}
                   \\hfill
                   \\adjustbox{valign=t}{",
                   paste0("\\includegraphics[width=.4\\linewidth]{figure/",
                           options[["label"]], "-1.pdf}}"), sep="\n")
    ## Was a codefig option supplied in chunk header?
    ## If so, wrap code block and graphical output with needed LaTeX code.
    if (!is.null(options$codefig)) {
      return(sprintf("%s %s %s", before, main, after))
    } else {
      return(main)
    }
}

knit_hooks[["set"]](chunk = codefigChunkHook)


## (3) TEMPLATE
##   codefig=TRUE is just one of several options needed for the
## side-by-side code block and a figure to come out right. Rather
## than typing out each of them in every single chunk header, we
## define a _template_ which bundles them all together. Then we can
## set all of those options simply by typing opts.label="codefig".

opts_template[["set"]](
codefig = list(codefig=TRUE, fig.show = "hide",
               r.opts = list(width=partWidth),
               tidy = TRUE,
               tidy.opts = list(width.cutoff = partWidth)))
@

A chunk without \texttt{opts.label="codefig"} set...
<<A>>=
1:60
@

\texttt{opts.label="codefig"} \emph{is} set for this one

<<B, opts.label="codefig", fig.width=8, cache=FALSE>>=
library(raster)
library(RColorBrewer)

## Create a factor raster with a nice RAT (Rast. Attr. Table)
r <- raster(matrix(sample(1:10, 100, replace=TRUE), ncol=10, nrow=10))
r <- as.factor(r)
rat <- levels(r)[[1]]
rat[["landcover"]] <- as.character(1:10)
levels(r) <- rat

## To get a nice grid...
p <- as(r, "SpatialPolygonsDataFrame")

## Plot it
plot(r, col = brewer.pal("Set3", n=10),
     legend = FALSE, axes = FALSE, box = FALSE)
plot(p, add = TRUE)
text(p, label =  getValues(r))
@

\texttt{opts.label="codefig"} not set, and all settings back to ``normal''.
<<C>>=
lm(mpg ~ cyl + disp + hp + wt + gear, data=mtcars)
@


\end{document}

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