r - HTML 中的 Knitr 和图形标题

Question

knitr 将参数 fig.cap 定义为

fig.cap: (NULL; character) figure caption to be used in a figure environment in LaTeX (in \caption{}); if NULL or NA, it will be ignored, otherwise a figure environment will be used for the plots in the chunk (output in \begin{figure} and \end{figure})

但是，对于 HTML 输出，以下工作:

---
title: "Caption Test"
author: "Some Author"
date: "February 18, 2016"
output: html_document
---

```{r}
library(ggplot2)
```

```{r, fig.cap = c("This is caption 1", "This is caption 2")}
## Plot 1
qplot(carat, price, data = diamonds)

## Plot 2
qplot(carat, depth, data = diamonds)
```

意思是，每个数字都有在代码块参数 fig.cap = c("Caption 1", "Caption 2") 中定义的正确标题

然而，当它们被放置在 block 选项中时，跟踪字幕是具有挑战性的——尤其是在长时间的情况下。除了为每个图形创建两个单独的 block 并在 block 外插入标题之外，还有其他选择吗？

Answer 1

您可以设置eval.after="fig.cap"以便在 block 运行后评估图形标题。这样，您可以在 block 内定义您的标题。

---
title: "Caption Test"
author: "Some Author"
date: "February 18, 2016"
output: html_document
---

```{r}
library(ggplot2)
library(knitr)
opts_knit$set(eval.after = 'fig.cap')
```

```{r, fig.cap = cap}
## Plot 1
qplot(carat, price, data = diamonds)
cap <- "This is caption 1"

## Plot 2
qplot(carat, depth, data = diamonds)

cap <- c(cap, "This is caption 2")
```