search_better_random: Search for a better projection using simulated annealing

In tourr: Tour Methods for Multivariate Data Visualisation

Search for a better projection using simulated annealing

Description

Given an initial t0, the cooling scheme updates temperature at

T = t0 /\log(i + 1)

The candidate basis is sampled via

B_j = (1 - \alpha) * B_i + \alpha * B

where alpha defines the neighbourhood, B_i is the current basis, B is a randomly generated basis The acceptance probability is calculated as

prob = \exp{-abs(I(B_i) - I(B_j))/ T}

For more information, see https://projecteuclid.org/download/pdf_1/euclid.ss/1177011077

Usage

search_better_random(
  current,
  alpha = 0.5,
  index,
  tries,
  max.tries = Inf,
  method = "linear",
  cur_index = NA,
  t0 = 0.01,
  ...
)

Arguments

current	starting projection
alpha	the angle used to search the target basis from the current basis
index	index function
tries	the counter of the outer loop of the opotimiser
max.tries	maximum number of iteration before giving up
method	whether the nearby bases are found by a linear/ geodesic formulation
cur_index	the index value of the current basis
t0	initial decrease in temperature
...	other arguments being passed into the search_better_random()

Examples

animate_xy(flea[, 1:6], guided_tour(holes(), search_f = search_better_random))

tourr documentation built on Aug. 25, 2023, 1:08 a.m.