R ggplot2 scale_discrete 离散数据的位置尺度

scale_x_discrete(..., expand = waiver(), guide = waiver(), position = "bottom")

scale_y_discrete(..., expand = waiver(), guide = waiver(), position = "left")

其他位置刻度：scale_x_binned()、scale_x_continuous()、scale_x_date()

ggplot(diamonds, aes(cut)) + geom_bar()


# \donttest{
# The discrete position scale is added automatically whenever you
# have a discrete position.

(d <- ggplot(subset(diamonds, carat > 1), aes(cut, clarity)) +
      geom_jitter())


d + scale_x_discrete("Cut")

d +
  scale_x_discrete(
    "Cut",
    labels = c(
      "Fair" = "F",
      "Good" = "G",
      "Very Good" = "VG",
      "Perfect" = "P",
      "Ideal" = "I"
    )
  )


# Use limits to adjust the which levels (and in what order)
# are displayed
d + scale_x_discrete(limits = c("Fair","Ideal"))
#> Warning: Removed 11189 rows containing missing values (`geom_point()`).


# you can also use the short hand functions xlim and ylim
d + xlim("Fair","Ideal", "Good")
#> Warning: Removed 9610 rows containing missing values (`geom_point()`).

d + ylim("I1", "IF")
#> Warning: Removed 16770 rows containing missing values (`geom_point()`).


# See ?reorder to reorder based on the values of another variable
ggplot(mpg, aes(manufacturer, cty)) +
  geom_point()

ggplot(mpg, aes(reorder(manufacturer, cty), cty)) +
  geom_point()

ggplot(mpg, aes(reorder(manufacturer, displ), cty)) +
  geom_point()


# Use abbreviate as a formatter to reduce long names
ggplot(mpg, aes(reorder(manufacturer, displ), cty)) +
  geom_point() +
  scale_x_discrete(labels = abbreviate)

# }