Graphics Reference
In-Depth Information
Setting the Positions of Tick Marks
Problem
You want to set where the tick marks appear on the axis.
Solution
Usually
ggplot()
does a good job of deciding where to put the tick marks, but if you want to
ggplot(PlantGrowth, aes(x
=
group, y
=
weight))
+
geom_boxplot()
ggplot(PlantGrowth, aes(x
=
group, y
=
weight))
+
geom_boxplot()
+
scale_y_continuous(breaks
=
c(
4
,
4.25
,
4.5
,
5
,
6
,
8
))
Figure 8-12. Left: box plot with automatic tick marks; right: with manually set tick marks
Discussion
The location of the tick marks defines where majorgrid lines are drawn. If the axis represents a
continuous variable, minorgrid lines, which are fainter and unlabeled, will by default be drawn
halfway between each major grid line.
You can also use the
seq()
function or the
:
operator to generate vectors for tick marks:
