Align plot areas in ggplot

Question

I am trying to use grid.arrange to display multiple graphs on the same page generated by ggplot. The plots use the same x data but with different y variables. The plots come

Answer 1

If you are using RMarkdown and knitting to PDF, I have an alternative approach. Knitr offers the functionality to plot subfigures when creating a PDF, which allows you to have multiple figures in a plot, each with their own caption.

For this to work, each plot has to be displayed separately. By joining together several functions from the cowplot package, I made the following function which aligns plots whilst keeping them as separate objects:

plot_grid_split <- function(..., align = "hv", axis= "tblr"){
  aligned_plots <- cowplot::align_plots(..., align=align, axis=axis)
  plots <- lapply(1:length(aligned_plots), function(x){
    cowplot::ggdraw(aligned_plots[[x]])
  })
  invisible(capture.output(plots))
}

Here is an example, comparing the layout normally vs using the function:

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

```{r}
plot_grid_split <- function(..., align = "hv", axis= "tblr"){
  aligned_plots <- cowplot::align_plots(..., align=align, axis=axis)
  plots <- lapply(1:length(aligned_plots), function(x){
    cowplot::ggdraw(aligned_plots[[x]])
  })
  invisible(capture.output(plots))
}
```

```{r fig-sub, fig.cap='Four Plots Not Aligned', fig.subcap=c('Plot One', 'Plot Two', 'Plot Three', 'Plot Four'), out.width='.49\\linewidth', fig.asp=1, fig.ncol = 2}  
library(ggplot2) 
plot <- ggplot(iris, aes(Sepal.Length, Sepal.Width, colour = Species)) +
  geom_point()

plot + labs(title = "A nice title")
plot + labs(caption = "A sample caption")
plot + theme(legend.position = "none")
plot + theme(legend.position = "top")
```  

```{r fig-sub-2, fig.cap='Four Plots Aligned', fig.subcap=c('Plot One', 'Plot Two', 'Plot Three', 'Plot Four'), out.width='.49\\linewidth', fig.asp=1, fig.ncol = 2}

x1 <- plot + labs(title = "A nice title")
x2 <- plot + labs(caption = "A sample caption")
x3 <- plot + theme(legend.position = "none")
x4 <- plot + theme(legend.position = "top")

plot_grid_split(x1, x2, x3, x4)
```

• You can learn more about subfigures in R within this post.
• In addition, you can check out the knitr options to read more about the chunk options for subfigures: https://yihui.name/knitr/options/