是否可以创建自渲染 Rmarkdown 文档？

Question

对于典型的 R 脚本，shebang 语法可用于在其中运行代码。带文件file.R

#!/usr/bin/env Rscript

<some R code here>

运行./file.R将执行代码。

但是可以用 R-markdown 以某种方式做同样的事情吗？因此，使用名为 的文件file.Rmd：

#!/usr/bin/env <some command>

<some markdown>
<some R code here>
<some markdown again>

跑步./file.Rmd会产生file.md?

Answer 1

您可以将 Rmd 文件视为 Rscript。例如，假设您的 Rmd 文件如下所示

---
title: "Untitled"
author: "ekoam"
date: "`r Sys.Date()`"
output: html_document
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

## R Markdown

This is an R Markdown document. Markdown is a simple formatting syntax for authoring HTML, PDF, and MS Word documents. For more details on using R Markdown see <http://rmarkdown.rstudio.com>.

When you click the **Knit** button a document will be generated that includes both content as well as the output of any embedded R code chunks within the document. You can embed an R code chunk like this:

```{r cars}
summary(cars)
```

## Including Plots

You can also embed plots, for example:

```{r pressure, echo=FALSE}
plot(pressure)
```

Note that the `echo = FALSE` parameter was added to the code chunk to prevent printing of the R code that generated the plot.

然后，您可以在该 Rmd 文件中添加以下代码

#!/usr/bin/env Rscript

args <- commandArgs()
fname <- normalizePath(sub("--file=", "", args[grepl("--file=", args)]))
thisfile <- readLines(fname)
newfname <- paste0(tempdir(), "/", basename(fname))
writeLines(thisfile[-1:-which(thisfile == "q(\"no\")")], newfname)
rmarkdown::render(newfname, output_dir = dirname(fname))
q("no")

这里的诀窍是q("no")。这一行终止了 R 会话，因此，在它之后写入的任何内容都将被忽略。这种效果也意味着编码的高度灵活性，因为在此之前您几乎可以编写任何有效的 R 代码q("no")。上面的代码只是创建了另一个临时 Rmd 文件，其内容与q("no"). 然后，我们rmarkdown::render将该临时文件并将输出转储到当前目录。

完整的 Rmd 文件如下所示

#!/usr/bin/env Rscript

args <- commandArgs()
fname <- normalizePath(sub("--file=", "", args[grepl("--file=", args)]))
thisfile <- readLines(fname)
newfname <- paste0(tempdir(), "/", basename(fname))
writeLines(thisfile[-1:-which(thisfile == "q(\"no\")")], newfname)
rmarkdown::render(newfname, output_dir = dirname(fname))
q("no")

---
title: "Untitled"
author: "ekoam"
date: "`r Sys.Date()`"
output: html_document
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

## R Markdown

This is an R Markdown document. Markdown is a simple formatting syntax for authoring HTML, PDF, and MS Word documents. For more details on using R Markdown see <http://rmarkdown.rstudio.com>.

When you click the **Knit** button a document will be generated that includes both content as well as the output of any embedded R code chunks within the document. You can embed an R code chunk like this:

```{r cars}
summary(cars)
```

## Including Plots

You can also embed plots, for example:

```{r pressure, echo=FALSE}
plot(pressure)
```

Note that the `echo = FALSE` parameter was added to the code chunk to prevent printing of the R code that generated the plot.