如何在 Rmarkdown 演示文稿（滑动）中回显代码之前显示块输出？

我最近开始在 Rmarkdown 中使用 Slidy 演示模板，并且喜欢每张幻灯片如何允许您向下滚动以获取更多内容。

我使用它的一种方法是与我的学生共享绘图（请参阅下面的示例代码）。在一张幻灯片上，我可以显示绘图以及用于创建绘图的确切代码，可以通过向下滚动来查看。

---
title: Echo Code Chunks After Code Results
subtitle: Thanks For Your Help
author: Me
date: "today"
output: slidy_presentation
runtime: shiny
---

## Slide with Interactive Plot

```{r, echo=TRUE, warning=FALSE, message=FALSE}
shinyApp(options = list(width = "100%", height = "700px"),
  ui = ( fluidPage(
inputPanel(
  selectInput("n_breaks", label = h3("Number of bins:"),
              choices = c(10, 20, 35, 50), selected = 20),

  sliderInput("bw_adjust", label = h3("Bandwidth:"),
              min = 0.2, max = 2, value = 1, step = 0.2)),
    plotOutput("stuff", height = "650px")

)),

server = function(input,output,session) {

  output$stuff = renderPlot({
  hist(faithful$eruptions, probability = TRUE, 
breaks = as.numeric(input$n_breaks),
xlab = "Duration (minutes)", main = "Geyser eruption duration", 
col = "bisque", border = 1)

  dens <- density(faithful$eruptions, adjust = input$bw_adjust, lwd = 2, col = "blue")
  lines(dens, col = "blue")
})
})
```

我遇到的问题是默认行为是在代码结果之前回显代码块，这与我想要的相反。

我显然可以通过插入两个代码块来解决这个问题，其中第一个代码块有块选项echo=FALSE第二个有echo=TRUE, fig.show='hide'但这需要我确保两个代码块匹配。如何反转此顺序以在回显代码之前显示绘图。

一如既往，感谢您的帮助。

您应该能够对演示文稿的正文执行您想要的操作。

## Slide with Interactive Plot

```{r thecode, echo=FALSE, warning=FALSE, message=FALSE}
shinyApp(options = list(width = "100%", height = "700px"),
  ui = (fluidPage(inputPanel(
    selectInput("n_breaks", label = h3("Number of bins:"), 
                choices = c(10, 20, 35, 50), selected = 20),
    sliderInput("bw_adjust", label = h3("Bandwidth:"), 
                min = 0.2, max = 2, value = 1, step = 0.2)),
    plotOutput("stuff", height = "650px"))),

server = function(input,output,session) {
  output$stuff = renderPlot({
    hist(faithful$eruptions, probability = TRUE, 
         breaks = as.numeric(input$n_breaks), xlab = "Duration (minutes)", 
         main = "Geyser eruption duration", col = "bisque", border = 1)
    dens <- density(faithful$eruptions, adjust = input$bw_adjust, 
                    lwd = 2, col = "blue")
    lines(dens, col = "blue")})
  })
```

```{r thecode, eval=FALSE}
```

That is:

• 创建两个具有相同名称的代码块（此处thecode).
• 在第一个代码块中，设置echo = FALSE这样代码就不会打印出来，但仍然会被评估。
• 在第二个代码块中，设置echo = TRUE，但保持该块完全为空（栅栏之间也没有空行）。