create_balls: Greedy Baller

In mappeR: Construct and Visualize TDA Mapper Graphs

Greedy Baller

Description

Make a greedy epsilon net of a data set.

Usage

create_balls(data, dists, eps)

Arguments

data	A data frame.
dists	A distance matrix for the data frame.
eps	A positive real number.

Value

A list of vectors of data point names, one list element per ball. The output is such that every data point is contained in a ball of radius \varepsilon, and no ball center is contained in more than one ball. The centers themselves are data points.

Examples

# Create a data set from 5000 points sampled from a parametric curve, plus some noise
num_points = 5000
P.data = data.frame(
  x = sapply(1:num_points, function(x)
    sin(x) * 10) + rnorm(num_points, 0, 0.1),
  y = sapply(1:num_points, function(x)
    cos(x) ^ 2 * sin(x) * 10) + rnorm(num_points, 0, 0.1),
  z = sapply(1:num_points, function(x)
    10 * sin(x) ^ 2 * cos(x)) + rnorm(num_points, 0, 0.1)
)
P.dist = dist(P.data)

# Ball it up
balls = create_balls(data = P.data, dists = P.dist, eps = .25)

mappeR documentation built on June 29, 2025, 1:07 a.m.