bookdown / rmarkdown / knitr：打开一个带有后续代码块（图形）结果的文档？

Question

想象一下简化的bookdown / rmarkdown文档，其内容如下：

---
title: "Test Doc"
author: "Balin"
date: "May 25, 2018"
output: 
  bookdown::pdf_document2:
    toc: no
---

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

<!-- Placeholder - See question -->

This stands in for an extensive report where `code`, its documentation
and interpretation of its results are integrated:

1. We load some data:
   ```{r data-loading}
    my_data <- cars
   ```

2. We (rougly) explore that data and report on it:
   ```{r data-exploration}
   summary(my_data)
   ```

3. We transform the data:
   ```{r data-transform}
   my_data <- log2(my_data)
   ```

4. ... many, many more steps ...

5. We perform a (central) graphical analysis:
   ```{r data-plot}
   plot(my_data)
   ```

6. We state some interpretation ... etc.

在这样的报告中，我的目标是将<!-- Placeholder - See question -->位替换为＆＃34;执行摘要＆＃34; /＆＃34; Sneak-Peak＆＃34; section，以chunk data-plot的图形输出为中心。这可以在bookdown / rmarkdown / knitr中实现，同时保持code /叙事整合给定相对定位吗？

Answer 1

是的，您可以使用knitr::fig_chunk()动态检索特定代码块中生成的图形的路径，例如，

---
title: "Test Doc"
author: "Balin"
date: "May 25, 2018"
output: 
  bookdown::pdf_document2:
    toc: no
---

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

# Executive Summary {-}

Here is an amazing discovery!

![](`r knitr::fig_chunk('data-plot', 'pdf')`)

# Detailed analysis

This stands in for an extensive report where `code`, its documentation
and interpretation of its results are integrated:

1. We load some data:
   ```{r data-loading}
    my_data <- cars
   ```

2. We (rougly) explore that data and report on it:
   ```{r data-exploration}
   summary(my_data)
   ```

3. We transform the data:
   ```{r data-transform}
   my_data <- log2(my_data)
   ```

4. ... many, many more steps ...

5. We perform a (central) graphical analysis:
   ```{r data-plot}
   plot(my_data)
   ```

6. We state some interpretation ... etc.

要使其适用于其他类型的输出格式，您可能需要更改文件扩展名pdf。一种方法可以是：

![](`r knitr::fig_chunk('data-plot', if (knitr::is_latex_output()) 'pdf' else 'png')`)

当然，这假设您将pdf设备用于LaTeX / PDF输出格式，并将png用于其他格式（这是R Markdown中图形设备的默认设置）。< / p>