paths_index: Compute index value for many histories.
In nspyrison/tourr: Implement Tour Methods in R Code

This is a convenience method that returns a data frame summarising the index values for multiple tour paths.

1	paths_index(bases_list, index_f)

`bases_list`	list of histories produced by `save_history`
`index_f`	index function to apply to each projection

holes1d <- guided_tour(holes, 1)
# Perform guided tour 5 times, saving results
tries <- replicate(5, save_history(flea[, 1:6], holes1d), simplify = FALSE)
# Interpolate between target bases
itries <- lapply(tries, interpolate)

paths <- paths_index(itries, holes)
head(paths)

if (require(ggplot2)) {
qplot(step, value, data=paths, group=try, geom="line")
qplot(step, improvement, data=paths, group=try, geom="line")
}