Pretty axis breaks inclusive of extreme values

This function returns pretty axis breaks that always include the extreme values of the data. This works by calling the extended Wilkinson algorithm (Talbot et al., 2010), constrained to solutions interior to the data range. Then, the minimum and maximum labels are moved to the minimum and maximum of the data range.

Usage

extended_range_breaks(n = 5, ...)

Arguments

n

Desired number of breaks.

...

Other arguments passed to the algorithm:

Q: set of nice numbers, by default c(1, 5, 2, 2.5, 4, 3).
w: weights applied to the four optimization components (simplicity, coverage, density, and legibility), by default c(0.25, 0.2, 0.5, 0.05).

Value

A function which takes a single argument, a vector of data, and returns the vector of axis label locations.

Details

extended_range_breaks() follows the conventions of the scales package: it returns a function that takes a vector of data and returns the breaks.

Note that ggplot2 hands a breaks function the expanded scale limits, not the data range. Passing extended_range_breaks() directly to breaks therefore places the end labels at the panel edges rather than at the extremes of the data. To label the extremes, which is what pairs with geom_rangeframe(), apply the function to the data instead: scale_x_continuous(breaks = extended_range_breaks()(mtcars$wt)).

References

Talbot, J., Lin, S., Hanrahan, P. (2010) An Extension of Wilkinson's Algorithm for Positioning Tick Labels on Axes, InfoVis 2010.

Author

Justin Talbot jtalbot@stanford.edu, Jeffrey B. Arnold, Baptiste Auguie

Examples

# Pretty breaks that always include the extremes of the data
extended_range_breaks()(mtcars$wt)
#> [1] 1.513 3.000 4.000 5.424

library(ggplot2)

ggplot(mtcars, aes(x = wt, y = mpg)) +
  geom_point() +
  geom_rangeframe() +
  scale_x_continuous(breaks = extended_range_breaks()(mtcars$wt)) +
  scale_y_continuous(breaks = extended_range_breaks()(mtcars$mpg)) +
  theme_tufte()