Axes - R Graphics - page 229

seq( 4 , 7 , by = .5 )
4.0 4.5 5.0 5.5 6.0 6.5 7.0
5 : 10
5 6 7 8 9 10
If the axis is discrete instead of continuous, then there is by default a tick mark for each item.
For discrete axes, you can change the order of items or remove them by specifying the limits
(see Changing the Order of Items on a Categorical Axis ). Setting breaks will change which of
the levels are labeled, but will not remove them or change their order. Figure 8-13 shows what
happens when you set limits and breaks :
# Set both breaks and labels for a discrete axis
ggplot(PlantGrowth, aes(x = group, y = weight)) + geom_boxplot() +
scale_x_discrete(limits = c( "trt2" , "ctrl" ), breaks = "ctrl" )
Figure 8-13. For a discrete axis, setting limits reorders and removes items, and setting breaks con-
trols which items have labels
See Also
To remove the tick marks and labels (but not the data) from the graph, see Removing Tick Marks
and Labels .