Two lines of X axis labels in ggplot

问题

I want to make two lines of X axis labels in ggplot.

In this plot, I want to add one more line of label below each specified year. Something like

1990 1995 2000 2005 2010 cold warm warm cold warm

This is my code for making this plot

ggplot(subset(dat, countryid %in% c("1")),  aes(date, 
nonpartisan))+geom_line(aes(color=countryid), color="dodgerblue1", 
size=1.4)+geom_line(aes(date, reshuffle), color="gray")+ theme_bw()

Is there any way to make one more line of label by creating a column specifically for the labels?

Thanks!

回答1:

You can just add custom labels via scale_x_continuous (or scale_x_date, if it is actually in Date format).

ggplot(subset(dat, countryid %in% c("1")),  aes(date, nonpartisan)) +
  geom_line(aes(color=countryid), color="dodgerblue1", size=1.4) +
  geom_line(aes(date, reshuffle), color="gray") + 
  theme_bw() +
  scale_x_continuous(name = 'date', 
                     breaks = c('1990', '1995', '2000', '2005', '2010'), 
                     labels = c('1990\ncold', '1995\nwarm', '2000\nwarm', '2005\ncold', '2010\nwarm'))

来源：https://stackoverflow.com/questions/27418222/two-lines-of-x-axis-labels-in-ggplot