如何在R块中布局字符值 [英] How to layout character value within R chunk

问题描述

在knitr软件包中，我喜欢kable函数.即使在R代码块中调用它，它也可以很好地布局表和类似对象的数据框架.现在，我想对一个字符值做同样的事情.有没有提供可以格式化的类似kable的输出("kprint")的功能?

knitr::kable() # exists for tables
knitr::kprint() # does a function like this exists for character values?

这就是我现在得到的:

print("character value") # within the R Chunk 

生成的报告中的输出:

## [1] "character value"

这就是我想要的，只是:

字符值

EDIT cat("character value")不是我要的解决方案，因为我不再需要R输出，而只是纯文本.

解决方案

要从R到TEX获取原始"字符串(没有任何格式或其他输出，例如[1])，有两件事要做:

• 使用块选项results = "asis"指示knitr不要修改输出.
• 使用cat而不是print，因为print将向量的长度加引号，并引用到输出中.

在这种情况下，使用\Sexpr{}的内联输出可能有用，因为默认情况下，\Sexpr{}会按原样打印:\Sexpr{myoutput}.

由于在注释中存在如何格式化输出的问题，这里有一些选择:

• 将LaTeX添加到传递给cat:cat("\\emph{foo}")的文本中.别忘了通过\逃脱\.

• 执行与上述相同的操作，但是使用函数来完成肮脏的工作":

  makeItNiceR <- function(x) {
    return(paste("\\fbox{\\texttt{", x, "}}"))
  }
  
  cat(makeItNiceR("foo bar is nice"))
  

  • (请注意，我们可以在makeItNiceR内使用cat来保存某些键入内容，但这会使函数的灵活性降低，因此我们无法再将其与\Sexpr{}结合使用.)

• 在\Sexpr{}周围手动添加LaTeX格式化命令:

  Add formatting to \emph{\Sexpr{myoutput}} directly in LaTeX.
  

• 组合makeItNiceR和\Sexpr{}以从\Sexpr{}获得格式正确的输出:

  \Sexpr{makeItNiceR(paste(myoutput, "is nice"))}
  

以下最少的示例演示了上面所有代码段的用法:

\documentclass{article}
\begin{document}

<<results = "asis">>=
makeItNiceR <- function(x) {
  return(paste("\\fbox{\\texttt{", x, "}}"))
}

myoutput <- "slim"

cat("foo")
cat("\\emph{foo}")
cat(makeItNiceR("foo bar is nice"))
@

\paragraph{Outside of chunk:} ~\\

\Sexpr{myoutput} \\

Add formatting to \emph{\Sexpr{myoutput}} directly in LaTeX. \\

\Sexpr{makeItNiceR(paste(myoutput, "is nice"))}
\end{document}

In the knitr package I like the kable function. It gives a nice layout of tables and data frame like objects even as it is called from within an R code chunk. Now I want to do the same thing with a character value. Is there a function that gives a kable-like output ("kprint") that can be formated?

knitr::kable() # exists for tables
knitr::kprint() # does a function like this exists for character values?

This is what I get now:

print("character value") # within the R Chunk 

Output in generated report:

## [1] "character value"

And this is what I want, just:

character value

EDIT cat("character value") is not the solution I am looking for because I don't want an R output anymore, but just a plain text.

解决方案

There are two things to do to get a "raw" character string (without any formatting or additional output like [1]) from R to TEX:

• Use the chunk option results = "asis" to instruct knitr not to modify the output.
• Use cat instead of print because print adds the lenght of the vector and quotes to the output.

In this context, inline output using \Sexpr{} might be useful because values in \Sexpr{} are by default printed "as they are": \Sexpr{myoutput}.

As there was the question of how to format the output in the comments, here some options:

• Add LaTeX to the text you pass to cat: cat("\\emph{foo}"). Don't forget to escape \ by an additional \.

• Do the same thing as above, but use a function to do the "dirty work":

  makeItNiceR <- function(x) {
    return(paste("\\fbox{\\texttt{", x, "}}"))
  }
  
  cat(makeItNiceR("foo bar is nice"))
  

  • (Note that we could use cat inside makeItNiceR to save some typing, but this makes the function less flexible and we cannot use it in combination with \Sexpr{} anymore.)

• Manually add LaTeX formatting commands around \Sexpr{}:

  Add formatting to \emph{\Sexpr{myoutput}} directly in LaTeX.
  

• Combine makeItNiceR and \Sexpr{} to get nicely formatted output from \Sexpr{}:

  \Sexpr{makeItNiceR(paste(myoutput, "is nice"))}
  

The following minimal examples demonstrates the usage of all code snippets from above:

\documentclass{article}
\begin{document}

<<results = "asis">>=
makeItNiceR <- function(x) {
  return(paste("\\fbox{\\texttt{", x, "}}"))
}

myoutput <- "slim"

cat("foo")
cat("\\emph{foo}")
cat(makeItNiceR("foo bar is nice"))
@

\paragraph{Outside of chunk:} ~\\

\Sexpr{myoutput} \\

Add formatting to \emph{\Sexpr{myoutput}} directly in LaTeX. \\

\Sexpr{makeItNiceR(paste(myoutput, "is nice"))}
\end{document}

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