cowplot: How to customize the gaps between main panel & marginal plots by modifying axis limits?
This is a followup question on one of the solutions provided by @ClausWilke (see post) to insert gap between main panel & marginal plots. How does one decide the (scale_x_continuous) limits? Also, what’ll happen if we used “NA” as the upper limit?
# Example with limits set to: (-2,4.5)
require(ggplot2)
require(cowplot)
pmain <- ggplot(data = mpg, aes(x = cty, y = hwy)) +
geom_point() +
xlab("City driving (miles/gallon)") +
ylab("Highway driving (miles/gallon)") +
theme_grey()
xbox2 <- axis_canvas(pmain, axis = "x", coord_flip = TRUE) +
geom_boxplot(data = mpg, aes(y = cty, x = 1)) +
scale_x_continuous(limits = c(-2, 4.5)) + coord_flip()
ybox2 <- axis_canvas(pmain, axis = "y") +
geom_boxplot(data = mpg, aes(y = hwy, x = 1)) +
scale_x_continuous(limits = c(-2, 4.5))
p1 <- insert_xaxis_grob(pmain, xbox2, grid::unit(0.8, "in"), position = "top")
p2 <- insert_yaxis_grob(p1, ybox2, grid::unit(0.8, "in"), position = "right")
ggdraw(p2)
With a continuous x-axis scale, you can use expand_limits to add some empty space between the main plot and the marginal plots.
For example, your ybox2 is a single box plot with a continuous x-axis scale. By default, the x-range for this plot is roughly 0.6 to 1.4 (you can see this by running ggplot(mpg, aes(y=hwy, x=1)) + geom_boxplot()). The following code sets the lower x-axis limit to 0.2 instead, meaning that about 0.4/(0.8+0.4) = 33% of the x-axis range will be the margin between the main plot and the marginal plot. We do the same for xbox2.
ybox2 <- axis_canvas(pmain, axis = "y") +
geom_boxplot(data = mpg, aes(y = hwy, x = 1)) +
expand_limits(x = 0.2)
xbox2 <- axis_canvas(pmain, axis = "x", coord_flip = TRUE) +
geom_boxplot(data = mpg, aes(y = cty, x = 1)) +
coord_flip() +
expand_limits(x = 0.2)
p1 <- insert_xaxis_grob(pmain, xbox2, grid::unit(0.4, "in"), position = "top")
p2 <- insert_yaxis_grob(p1, ybox2, grid::unit(0.4, "in"), position = "right")
ggdraw(p2)
