how to prevent axes from intersecting in ggplot2

Question

I'm using ggplot2 to make line graphs of some log-transformed data that all have large values (between 10^6 and 10^8); since the axes doesn't start at zero, I'd prefer not to have them intersect at the "origin."

Here's what the axes currently look like:

I'd prefer something more like one gets from base graphics (but I'm additionally using geom_ribbon and other fancy things I really like in ggplot2, so I'd prefer to find a ggplot2 solution):

Here's what I'm doing currently:

mydata <- data.frame(Day = rep(1:8, 3), 
  Treatment = rep(c("A", "B", "C"), each=8), 
  Value = c(7.415929, 7.200486, 7.040555, 7.096490, 7.056413, 7.143981, 7.429724, 7.332760, 7.643673, 7.303994, 7.343151, 6.923636, 6.923478, 7.249170, 7.513370, 7.438630, 7.209895, 7.000063, 7.160154, 6.677734, 7.026307, 6.830495, 6.863329, 7.319219))

ggplot(mydata, aes(x=Day, y=Value, group=Treatment)) 
  + theme_classic() 
  + geom_line(aes(color = Treatment), size=1) 
  + scale_y_continuous(labels = math_format(10^.x)) 
  + coord_cartesian(ylim = c(6.4, 7.75), xlim=c(0.5, 8))

plot(mydata$Day, mydata$Value, frame.plot = F)  #non-intersecting axes

Chargeable

So you want something more like the bottom plot? You could try geom_point or qplot? – Cording

Answer 1

Workaround for this problem would be to remove axis lines with theme(axis.line=element_blank()) and then add false axis lines with geom_segment() - one for x axis and second for y axis. x, y , xend and yend values are determined from your plot (taken as the smallest and the largest values shown on plot for each corresponding axis) and axis limits used in coord_cartesian() (minimal value of limits to ensure that segment is plotted in place of axis).

ggplot(mydata, aes(x=Day, y=Value, group=Treatment)) +theme_classic() +
 geom_line(aes(color = Treatment), size=1) +
 scale_y_continuous(labels = math_format(10^.x))+ 
 coord_cartesian(ylim = c(6.4, 7.75), xlim=c(0.5, 8))+
 theme(axis.line=element_blank())+
 geom_segment(x=2,xend=8,y=6.4,yend=6.4)+
 geom_segment(x=0.5,xend=0.5,y=6.5,yend=7.75)

Sprite

Answer 2

An older question. But since I was looking for this functionality recently I thought I'd flag the ggh4x package, which adds guides for truncating axes.

library(ggh4x)
#> Loading required package: ggplot2

ggplot(data.frame(x=0:10, y=0:10), aes(x, y)) +
  geom_point() +
  theme_classic() +
  guides(x = "axis_truncated", y = "axis_truncated")

^{Created on 2023-02-17 with reprex v2.0.2}

Apart from convenience, two nice things about the ggh4x option are that 1) it is stable across more complex plot compositions like faceting and 2) its dependencies are a subset of those belonging to ggplot2, so you aren't introducing a bunch of additional imports.

P.S. There's an open GitHub issue to bring this kind of "floating axes" functionality to the main ggplot2 library. It looks like it will eventually be incorporated.

Quartered