Individual axis limits with scale(expand) and scale=free in facetted ggplots - r

Question

library(ggplot2)
df <- data.frame(Treatment=c("A", "B","A","B"), Value=c(3,4, 20,2), SE=c(1,1,5,1), Type=c("c1","c1","c2","c2"))
p1 <- ggplot(df, aes(Treatment, Value,fill=Treatment)) +
geom_bar(stat="identity", col="Black") +
geom_errorbar(aes(ymax = Value + SE, ymin=Value), col="black") +
facet_wrap(~Type, scale="free_y") +
theme(panel.background = element_blank(),
panel.border = element_rect(colour = "black", fill=NA),
strip.background = element_blank())
p1
I want to remove the white space between bar and x-axis:
p1 + scale_y_continuous(expand = c(0,0))
This also removes white space between the geom and the maximum of the y-axis. One way to prevent this is to control the limits of the y-axis
p1 + scale_y_continuous(expand = c(0,0), limits=c(0,26))
But now panel c1 has lots of white space, as limits apparently overrides scale="free", which is especially irrating when the panels are arranged in columns.
So, i need to have the expand-argument and scale="free" active at the same time. Is it possible?

Answer 1

You may want to use a geom_blank():
Please be considerate and try not to confound the user! This type of transformation can be dangerous!
library(ggplot2)
df <- data.frame(Treatment=c("A", "B","A","B"), Value=c(3,4, 20,2), SE=c(1,1,5,1), Type=c("c1","c1","c2","c2"))
ggplot(df, aes(Treatment, Value,fill=Treatment)) +
geom_bar(stat="identity", col="Black") +
geom_errorbar(aes(ymax = Value + SE, ymin=Value), col="black") +
geom_blank(aes(y=Value + SE + 1)) +
facet_wrap(~Type, scale="free_y") +
theme(panel.background = element_blank(),
panel.border = element_rect(colour = "black", fill=NA),
strip.background = element_blank()) +
scale_y_continuous(expand = c(0,0))
Or:
ggplot(df, aes(Treatment, Value,fill=Treatment)) +
geom_bar(stat="identity", col="Black") +
geom_errorbar(aes(ymax = Value + SE, ymin=Value), col="black") +
geom_blank(aes(y=Value + 2 * SE)) +
facet_wrap(~Type, scale="free_y") +
theme(panel.background = element_blank(),
panel.border = element_rect(colour = "black", fill=NA),
strip.background = element_blank()) +
scale_y_continuous(expand = c(0,0))
Created on 2018-05-17 by the reprex package (v0.2.0).