我正在用 R markdown 编写一份带有 pdf 输出的报告。我有几个图，我想在 2x2 矩阵中每页显示四个图。有没有办法让它们像这样显示并带有单独的标题？

这是我到目前为止所尝试过的：

• 包 gridExtra - 我可以轻松设置我想要的布局，但我无法向图中添加标题。是否有一个选项可以向图中添加标题grid.arrange?

• 将每个图放在不同的块中并使用 R 块选项。基本设定out.width='.49\\linewidth', fig.align='right' and fig.align='left'或者。在这里我可以设置单独的标题fig.cap但这些图总是显示在单独的页面上。

• 我尝试玩fig.width and fig.height选项，并能够让它们显示在同一页面上各自的左侧或右侧。但是，标题始终采用整个页面宽度并保持在中心位置，而不是随绘图大小环绕。有没有办法让标题遵循绘图大小规则？

这是示例代码：

```{r, echo=FALSE, cache=FALSE, results=FALSE, warning=FALSE,  comment=FALSE, message= FALSE, eval =T, fig.height= 9}

p1<- ggplot(mpg, aes(displ, hwy, colour = class)) + 
geom_point()+
labs(caption = "Lorem ipsum dolor sit amet, consectetur adipiscing     elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. ")+
theme(plot.caption = element_text(hjust = 0.5))

p2<- ggplot(mpg, aes(displ, hwy, colour = class)) + 
geom_point()+
labs(caption = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.  ")+
theme(plot.caption = element_text(hjust = 0.5))

p3<- ggplot(mpg, aes(displ, hwy, colour = class)) + 
geom_point()+
labs(caption = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. ")+
theme(plot.caption = element_text(hjust = 0.5))

p4<- ggplot(mpg, aes(displ, hwy, colour = class)) + 
geom_point()+
labs(caption = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. ")+
theme(plot.caption = element_text(hjust = 0.5))

library(gridExtra)
grid.arrange(p1,p2,p3,p4)
```

I'd appreciate any help. Thanks!

您可以在 LaTeX 输出中使用子图，如下所述here https://stackoverflow.com/questions/12546365/subfigures-or-subcaptions-with-knitr/49086985#49086985。如果您有很多绘图并且希望更容易地提供标题，您可以在列表中指定这些标题（即captions <- c("Caption 1", "Caption 2") 在块之前并将此列表提供给块作为fig.subcap=captions

---
output: pdf_document
header-includes:
  - \usepackage{subfig}
---  

```{r}
captions <- c("Caption 1",
              "Caption 2", 
              "Caption 3",
              "Caption 4: a very very very very very very very very very long one")
```


```{r, echo=FALSE, cache=FALSE, results=FALSE, warning=FALSE,  comment=FALSE, message= FALSE, eval =T,  fig.cap = "Overall Caption", fig.subcap=captions, out.width='.49\\linewidth', fig.asp=1, fig.ncol = 2}
library(ggplot2)
p1<- ggplot(mpg, aes(displ, hwy, colour = class)) + 
geom_point()+
theme(plot.caption = element_text(hjust = 0.5))

p2<- ggplot(mpg, aes(displ, hwy, colour = class)) + 
geom_point()+
theme(plot.caption = element_text(hjust = 0.5))

p3<- ggplot(mpg, aes(displ, hwy, colour = class)) + 
geom_point()+
theme(plot.caption = element_text(hjust = 0.5))

p4<- ggplot(mpg, aes(displ, hwy, colour = class)) + 
geom_point()+
theme(plot.caption = element_text(hjust = 0.5))

p1
p2
p3
p4
```

Edit

为了确保子图之间有边距，您可以添加margins加载包时的选项：

  - \usepackage[margin = 8pt]{subfig}

查看包文档中的其他选项：http://anorien.csc.warwick.ac.uk/mirrors/CTAN/macros/latex/contrib/subfig/subfig.pdf http://anorien.csc.warwick.ac.uk/mirrors/CTAN/macros/latex/contrib/subfig/subfig.pdf