How can I scale nested plot_grid to the same size?

Question

I have 7 plots and I organize them in 2 columns, one with 3 plots and other one with 4 plots. I used plot_grid from cowplot for that. The result is almost perfect, however, the column with 3 plots has bigger plots. How can I scale this column to get the same size in all plots and align the first and the last plot of each column?

library(ggplot2)
library(cowplot)

Value <- seq(0,1000, by = 1000/10)
Index <- 0:10
DF <- data.frame(Index, Value)

plot1 <- ggplot(DF, aes(x = Index, y = Value)) +
  geom_line(linetype = 2) +
  theme(aspect.ratio = 0.5)

plot2 <- ggplot(DF, aes(x = Index, y = Value)) +
  geom_line(linetype = 2) +
  theme(aspect.ratio = 0.5)

plot3 <- ggplot(DF, aes(x = Index, y = Value)) +
  geom_line(linetype = 2) +
  theme(aspect.ratio = 0.5)

plot4 <- ggplot(DF, aes(x = Index, y = Value)) +
  geom_line(linetype = 2) +
  theme(aspect.ratio = 0.5)

plot5 <- ggplot(DF, aes(x = Index, y = Value)) +
  geom_line(linetype = 2) +
  theme(aspect.ratio = 0.5)

plot6 <- ggplot(DF, aes(x = Index, y = Value)) +
  geom_line(linetype = 2) +
  theme(aspect.ratio = 0.5)

plot7 <- ggplot(DF, aes(x = Index, y = Value)) +
  geom_line(linetype = 2) +
  theme(aspect.ratio = 0.5)

col1 <- plot_grid(plot1, plot2, plot3, align = "v", ncol = 1)
col2 <- plot_grid(plot4, plot5, plot6, plot7, align = "v", ncol = 1)
plot_grid(col1, col2, ncol = 2, align = "hv")

Answer 1

You can place a null plot into your first column:

col1 <- plot_grid(plot1, plot2, plot3, NULL, align = "v", ncol = 1)

However, to me, this is not a case for a nested plot grid. Nested plot grids are specifically for the purpose of combining plots with complex arrangements, e.g. one plot in one column spanning two rows in another column. For what you want, I would do a single plot_grid() call, just like the other comment suggests:

plot_grid(plot1, plot4, plot2, plot5, plot3, plot6, NULL, plot7,
          ncol = 2, align = "hv")

Please also note that the align option doesn't work when you specify a particular aspect ratio. You can either specify an aspect ratio or align. In most cases, it's not necessary to specify an aspect ratio, you can do that when saving the figure. The function save_plot() in particular takes an aspect ratio option (applied to the whole image, though, not the plot area).