ggplot2 - Correctly arrange odd number of plots into one figure

Question

I have an odd number of plots to arrange into one figure and I desire to show the last plot centered in the last row of the figure.

Here some sample data:

Answer 1

This uses grid and gridExtra to place the plots on a 2×4 matrix layout. Each of your plots occupies two "slots". The two outer "slots" on the bottom row are plotted as NULL grobs to centre your plot.

# Convert to grobs
lst_p <- lapply(lst_p, ggplotGrob)

# Plot using gridExtra and grid
gridExtra::grid.arrange(lst_p[[1]], lst_p[[2]], grid::nullGrob(), lst_p[[3]], grid::nullGrob(),
                        layout_matrix = matrix(c(1,1,2,2,3,4,4,5), byrow = TRUE, ncol = 4))

Answer 2

Using nested cowplot::plot_grids:

library(ggplot2)
set.seed(99)

x_1 = data.frame(z = rnorm(100))
x_2 = data.frame(z = rnorm(100))
x_3 = data.frame(z = rnorm(100))

lst = list(x_1, x_2, x_3)

lst_p = list()

for (i in 1:length(lst)) {
    lst_p[[i]] = ggplot(data=lst[[i]], aes(lst[[i]]$z)) + 
    geom_histogram() +
        xlab("X LAB") +
        ylab("Y LAB") 
}


p_no_labels = lapply(lst_p, function(x) x + xlab("") + ylab(""))

title = cowplot::ggdraw() + cowplot::draw_label("test", size = 20)
top_row = cowplot::plot_grid(p_no_labels[[1]], p_no_labels[[2]], ncol=2)
bottom_row = cowplot::plot_grid(NULL, p_no_labels[[2]], NULL, ncol=3, rel_widths=c(0.25,0.5,0.25))

cowplot::plot_grid(title, top_row, bottom_row, ncol=1, rel_heights=c(0.1,1,1))

Answer 3

A not-terribly elegant solution would be to leave the middle plot empty on the first row:

p_no_labels2<-list(p_no_labels[[1]],NULL,p_no_labels[[2]],NULL,p_no_labels[[3]])
p_grid = cowplot::plot_grid(plotlist = p_no_labels2, ncol = 3) 

Answer 4

You can use gridExtra::grid.arrange for this. All you need to do is specify the layout of the plots with a layout matrix.

library(ggplot2)
set.seed(99)

x_1 = data.frame(z = rnorm(100))
x_2 = data.frame(z = rnorm(100))
x_3 = data.frame(z = rnorm(100))

lst = list(x_1, x_2, x_3)

lst_p = list()

for (i in 1:length(lst)) {
lst_p[[i]] = ggplot(data=lst[[i]], aes(lst[[i]]$z)) + 
geom_histogram() +
xlab("X LAB") +
ylab("Y LAB") 
}

p_no_labels = lapply(lst_p, function(x) x + xlab("") + ylab(""))


#layout of plots

lay <- rbind(c(1,2),c(1,2),
              c(3,3))



#arrange the grid and specify the `layout_matrix`
gridExtra::grid.arrange(grobs=p_no_labels, layout_matrix=lay)