'Labels on top' with facet_grid, or 'space option' with facet_wrap

Question

facet_grid allow me to size each facet width according to number of items on y axis ( space argument):

df <- data.frame(label = c("Variable one", rep("Variable two", 2), rep("Variable three", 3)), item = c("A", "B", "C", "D", "E", "F"), value = rnorm(6))
ggplot(df, aes(x = value, y = item)) + 
geom_point() + 
facet_grid(label ~ ., scales = "free_y", space = "free_y") + 
ylab("") + 
theme(strip.text.y = element_text(angle=0))

But I would like facet labels on top, so I switch to facet_wrap , and lost the space argument (facets have all the same width):

ggplot(df, aes(x = value, y = item)) + 
geom_point() + 
facet_wrap(~ label, scales = "free_y", ncol = 1) + 
ylab("")

Is it possible to obtain the best of both worlds?

Thank you in advance for your help.

Answer 1

It can be done manually. The ratio of the heights of the three panels in the desired plot is roughly 1:3:2. The heights of the three panels can be adjusted by changing the grobs:

library(ggplot2)
library(grid)
df <- data.frame(label = c("Variable one", rep("Variable two", 2), rep("Variable three", 3)), item = c("A", "B", "C", "D", "E", "F"), value = rnorm(6))

p1 = ggplot(df, aes(x = value, y = item)) + 
geom_point() + 
facet_wrap(~ label, scales = "free_y", ncol = 1) + 
ylab("")

g1 = ggplotGrob(p1) 

g1$heights[[7]] = unit(1, "null")
g1$heights[[12]] = unit(3, "null")
g1$heights[[17]] = unit(2, "null")

grid.newpage()
grid.draw(g1)

Or, the heights can be set to be the same as those in the original plot:

p2 = ggplot(df, aes(x = value, y = item)) + 
geom_point() + 
facet_grid(label ~ ., scales = "free_y", space = "free_y") + 
ylab("") + 
theme(strip.text.y = element_text(angle=0))

g2 = ggplotGrob(p2) 

g1$heights[[7]] = g2$heights[[6]]
g1$heights[[12]] = g2$heights[[8]]
g1$heights[[17]] = g2$heights[[10]]

grid.newpage()
grid.draw(g1)

Or, the heights can be set without reference to the original plot. They can be set according to the number of items for each label in df . And borrowing some code from @baptiste's answer here to select the items from the layout corresponding to the panels:

# From 'df', get the number of 'items' for each 'label'.
# That is, the number y-breaks in each panel.
library(plyr)
N = dlply(df, .(label), function(x) length(row.names(x)))

# Get the items in the g1 layout corresponding to the panels.
panels1 <- g1$layout$t[grepl("panel", g1$layout$name)]

# Replace the default panel heights with relative heights
g1$heights[panels1] <- unit(N, "null")

## Draw g1
grid.newpage()
grid.draw(g1)

Answer 2

I don't think this feature exists or is planning on being implemented in ggplot2 ( see here for the closed issue discussing this feature )

However the ggforce package supports what you're looking for

library(ggplot2)
library(ggforce)
df <- data.frame(label = c("Variable one", rep("Variable two", 2), rep("Variable three", 3)), item = c("A", "B", "C", "D", "E", "F"), value = rnorm(6))
  
ggplot(df, aes(x = value, y = item)) + 
  geom_point() + 
  ggforce::facet_col(facets = vars(label), 
                     scales = "free_y", 
                     space = "free") +
  ylab("") + 
  theme(strip.text.y = element_text(angle=0))

^{Created on 2020-06-28 by the reprex package (v0.3.0)}

Answer 3

I don't know how to do it in ggplot , but you may achieve a similar layout with a ggplot oid style using latticeExtra :

library(latticeExtra)
df$label <- factor(df$label, levels = unique(df$label))

dotplot(item ~ value | label, data = df,
        layout = c(1, 3),
        as.table = TRUE,
        scales = list(y = list(relation = "free")),
        par.settings = ggplot2like())
resizePanels()