探索labs()函数：增加标题，更改坐标名称用。

p <- ggplot(mtcars, aes(mpg, wt, colour = cyl)) + geom_point()
p
p + labs(colour = "Cylinders")#颜色标签改名
p + labs(x = "New x label")#X轴改名

#主副坐标在图左上方显示
p + labs(title = "New plot title")
p + labs(title = "New plot title", subtitle = "A subtitle")

# The caption appears in the bottom-right, and is often used for
# sources, notes or copyright
p + labs(caption = "(based on data from ...)")

# The plot tag appears at the top-left, and is typically used
# for labelling a subplot with a letter.
p + labs(title = "title", tag = "A")

# If you want to remove a label, set it to NULL.
p + labs(title = "title") + labs(title = NULL)