This is a novel method for finding more interesting projections for the
guided tour. It works by first taking a small step in n random
directions, and then picking the direction that looks most promising
(based on the height of the index function). Once the best direction is
found, it performs a linear search along the geodesic in that direction,
traveling up to half way around the sphere.
search_geodesic(current, alpha = 1, index, max.tries = 5, n = 5,
stepS = 0.01, cur_index = NA)starting projection
maximum distance to travel (currently ignored)
interestingness index function
maximum number of failed attempts before giving up
number of random steps to take to find best direction
step size for evaluation of best direction
index value for starting projection, set NA if it needs to be calculated
You should not to have call this function directly, but should supply it
to the guided_tour as a search strategy.