combine and align ggplot, including one square with control of their height

Question

I'm trying to vertically align several ggplots, including one that must be square (using coord_fixed or any other means). I also want to be able to control the relative heights of the different plots. The desired plot look would like this, the number of rectangular: (wanted plot). The number of rectangular plots beneath the square one can vary from 1 to 5.

I've read other SO threads, including this one (Vertically align of plots of different heights using cowplot::plot_grid() when using coord_equal()).

So far: I can align plots, including with one that is square (with egg or patchwork) but I don't manage to adjust the relaive heights of the panels. Below is what I tried (using cowplot, egg or patchwork packages).

Using coord_fixed

#data
a = data.frame(x = seq(0,10), y = seq(10,20), z = runif(11))
b = data.frame(x = seq(0,10), y = runif(11))

#generate ggplot
library(ggplot2)
p1 = ggplot(a, aes(x = x, y = y, fill = z)) + geom_raster() + coord_fixed()
p2 = ggplot(b, aes(x = x, y = y)) + geom_line()


#align with cowplot => alignment not working if p1 is squared.
library(cowplot)
plot_grid(p1,p2,p2, ncol = 1, align = 'v', axis = 'lr')

#align with patchwork => working with p1 squared, but can't control the relative heights
library(patchwork)
p1 + p2 + p2 + plot_layout(nrow = 3)              #aligned, p1 being square
p1 + p2 + p2 + plot_layout(nrow = 3, 
                           heights = c(3, 1, 1))  #not aligned

#same, it does not seem to work with egg.
library(egg)
egg::ggarrange(p1, p2, p2, ncol = 1) 
egg::ggarrange(p1, p2, p2, ncol = 1, heights = c(3,1,1))

--

A alternative strategy would be to not use coord_fixed for p1, play with the export file dimensions and export at the "right" dimensions

p1bis = ggplot(a, aes(x = x, y = y, fill = z)) + geom_raster()
plot_grid(p1bis,p2,p2, ncol = 1, align = 'v', axis = 'lr', rel_heights = c(4,1,1))
ggsave("temp.pdf", width = 18, height = 24.5, units = "cm")

But I'm not clear on how to calculate the width:height ratio of the export PDF document in a dynamic manner. Is there a way to extract (in npc units?) the width and height of the panel.border?

--

I also came across the ggh4x package, which, like egg, contains a function to set the panel size. But the panelsize information seems to be lost when combining with patchwork

library(ggh4x)
p1f = p1bis + force_panelsizes(rows = unit(10, "cm"), cols = unit(10, "cm"))
p2f = p2    + force_panelsizes(cols = unit(10, "cm"), rows = unit(3, "cm"))
p1f + p2f + p2f + plot_layout(nrow = 3)

Do you have any other ideas? Am I missing something trivial somewhere?

Thanks for your time !

Answer 1

The case of fixed aspects plots is described on the {patchwork} website:

A special case when it comes to assembling plots are when dealing with fixed aspect plots, such as those created with coord_fixed(), coord_polar(), and coord_sf(). It is not possible to simultaneously assign even dimensions and align fixed aspect plots.

...

Which solution is needed is probably dependent on the specific use case.

In your case one way to do it, would be to nest the plots:

library(ggplot2)
library(patchwork)

p22 <- p2 + p2 + plot_layout(nrow = 2)      
p1 + p22 + plot_layout(nrow = 2)

^{Created on 2021-05-11 by the reprex package (v0.3.0)}

This gives no fine tuned control over the heights, but we could adjust the nested plots using plot_spacer()s:

library(patchwork)

p22 <- plot_spacer() + p2 + plot_spacer() + p2 + plot_spacer() + plot_layout(heights = c(1, 2, 1, 2, 1))      

p1 + p22 + plot_layout(nrow = 2)

^{Created on 2021-05-11 by the reprex package (v0.3.0)}