Sample the original data with replacement and fit LOWESS curves accordingly.
We keep on resampling the data and finally we will see several bootstrapped
LOWESS curves, which may give us a rough idea about a confidence interval
of the LOWESS fit.
library(animation)
ani.options(nmax = 100, interval = 0.02)
boot.lowess(cars, pch = 20, xlab = "speed", ylab = "dist")
boot.lowess(cars, f = 1/3, pch = 20)