How can I align multiple plots by their titles instead of plot area?

Question

I\'m using egg to align multiple plots on a page. I\'m wondering if it\'s possible to align two columns by the titles a) and c) instead of plot are

Answer 1

Adding a blank dummy faceting variable to plot p1/ a) seems like the easiest solution

p1 <- ggplot(data.frame(mtcars, dummy=''), 
             aes(mpg, wt, colour = factor(cyl))) +
  geom_point() + ggtitle("a)") +
  facet_wrap(~dummy)

Answer 2

I found another way by using cowplot package

left_col <- cowplot::plot_grid(p1 + ggtitle(""), p2 + ggtitle(""), 
                               labels = c('a)', 'b)'), label_size = 14,
                               ncol = 1, align = 'v', axis = 'lr') 
cowplot::plot_grid(left_col, p3 + ggtitle(""), 
                   labels = c('', 'c)'), label_size = 14,
                   align = 'h', axis = 'b')

See also here

Edit:

A recently developed package patchwork for ggplot2 can also get the job done

library(patchwork)

{
  p1 + {p2} + patchwork::plot_layout(ncol = 1)
} / p3 + patchwork::plot_layout(ncol = 2)