Centre a plot to the middle of a page using Knitr

Question

I'd like to align a plot to the center of a page of a knitr-generated pdf document. I can horizontally align the plot to the center using fig.align='center' but can't figure out how to get the plot vertically aligned to the center.

I've been using the following code:

---
header-includes: \usepackage{graphicx}
output: 
  pdf_document
geometry:
  left=1in,right=1in,top=1in,bottom=1in
---


```{r,fig.align='center',out.extra='angle=90', echo=FALSE}

library(ggplot2)
ggplot(diamonds, aes(y=carat, x=price, colour=clarity))+geom_point()+
facet_wrap(~cut)

```

Solution

On the LaTeX side, a vertically centered figure must be a figure with position p. How this can be achieved using knitr depends:

• If the figure has a caption, it is placed in a figure environment (see fig.env). Then only the additional option fig.pos = 'p' is needed.

• If the figure has no caption (which is usually bad), you can manually add the figure environment:

  \begin{figure}[p]
  
  ```{r,fig.align='center',out.extra='angle=90', echo=FALSE}
  
  library(ggplot2)
  ggplot(diamonds, aes(y=carat, x=price, colour=clarity))+geom_point()+
  facet_wrap(~cut)
  
  ```
  \end{figure}
  

Note that this works when compiling to PDF but restricts you to PDF as output format.

Comments

[nad7wf]

I've spent several days (literally) trying to figure out how to knit a pdf with many images, but have only one image per page and vertically centered. I finally came across your solution for a single figure, but I'm having trouble adapting it for many images. Please help! :)

[CL.]

@nad7wf Have a look at this gist; I think it might solve your problem. If not, please open a new question (and ping me here so I get a notification). Hope that helps!