ggplot2 R fix x-axis label at a specific point relative to plot

问题

Say I have a plot like this:

library(ggplot2)
dat <- data.frame(x = 1:10, y = 1:10)

ggplot(dat, aes(x = x, y = y)) +
  geom_point() +
  xlab("Test label")

Does ggplot2 allow for fixing the xlab positioning at a specific point? Say I wanted the label to appear centered at the point where x = 7 (rather than the default centering).

回答1:

This isn't exactly what you want, but you can adjust the horizontal justification in the theme options. This is relative between 0 and 1, not tied to the data coordinates. 0 is left-justified (left side of the axis), 1 is right-justified, and the default 0.5 as centered. In this case, we can set hjust = 0.7. (Though an axis from 1 to 10 has length 10 - 1 = 9, so we could get nitpicky and use (7 - 1) / (10 - 1) = 2/3... I'll leave it to you how precise you want to be.)

ggplot(dat, aes(x = x, y = y)) +
  geom_point() +
  xlab("Test label") +
  theme(axis.title.x = element_text(hjust = 0.7))

回答2:

Here is another way, but the one from @Gregor Thomas is nicer

library(ggplot2)
dat <- data.frame(x = 1:10, y = 1:10, label = 'Test label')

p <- ggplot(dat, aes(x = x, y = y)) +
  geom_point() + 
  xlab('')             # no x-label
  #xlab("Test label")

p + geom_text(aes(label = label, x = 7, y = -Inf), vjust = 3) + 
  coord_cartesian(clip = 'off')    # This keeps the labels from disappearing

来源：https://stackoverflow.com/questions/65616313/ggplot2-r-fix-x-axis-label-at-a-specific-point-relative-to-plot