Connects the points of a Pareto front (also known as Pareto frontier) and hence visualizes the dominance region of a Skyline.
Usage
plot_front(df, pref, ...)
Arguments
df
The data frame for which the Pareto front is plotted. This may be already a maximal set w.r.t. the preference pref,
but anyway the maximal set is recalculated via psel(df, pref).
pref
The preference representing the Skyline goals. This must be a Pareto composition (p1 * p2) or
intersection composition (p1 | p2) of
two low or high preferences.
...
Additional graphic parameters which are passed to the segments function (internally used to plot the front).
Details
plot_front assumes that there is an existing plot, where the value of the first preference was plotted as x-coordinate
and the value of the second preference as y-coordinate.
Examples
# plots Pareto fronts for the hp/mpg values of mtcars
show_front <- function(pref) {
plot(mtcars$hp, mtcars$mpg)
sky <- psel(mtcars, pref)
plot_front(mtcars, pref, col = rgb(0, 0, 1))
points(sky$hp, sky$mpg, lwd = 3)
}
# do this for all four combinations of Pareto compositions
show_front(low(hp) * low(mpg))
show_front(low(hp) * high(mpg))
show_front(high(hp) * low(mpg))
show_front(high(hp) * high(mpg))
# compare this to the front of a intersection preference
show_front(high(hp) | high(mpg))