dbscan (version 1.2-0)

comps: Find Connected Components in a Nearest-neighbor Graph

Description

Generic function and methods to find connected components in nearest neighbor graphs.

Usage

comps(x, ...)
# S3 method for dist
comps(x, eps, ...)
# S3 method for kNN
comps(x, mutual = FALSE, ...)
# S3 method for sNN
comps(x, ...)
# S3 method for frNN
comps(x, ...)

Value

a integer vector with component assignments.

Arguments

x

the NN object representing the graph or a dist object

...

further arguments are currently unused.

eps

threshold on the distance

mutual

for a pair of points, do both have to be in each other's neighborhood?

Author

Michael Hahsler

Details

Note that for kNN graphs, one point may be in the kNN of the other but nor vice versa. mutual = TRUE requires that both points are in each other's kNN.

See Also

Other NN functions: NN, frNN(), kNN(), kNNdist(), sNN()

Examples

set.seed(665544)
n <- 100
x <- cbind(
  x=runif(10, 0, 5) + rnorm(n, sd = 0.4),
  y=runif(10, 0, 5) + rnorm(n, sd = 0.4)
  )
plot(x, pch = 16)

# Connected components on a graph where each pair of points
# with a distance less or equal to eps are connected
d <- dist(x)
components <- comps(d, eps = .8)
plot(x, col = components, pch = 16)

# Connected components in a fixed radius nearest neighbor graph
# Gives the same result as the threshold on the distances above
frnn <- frNN(x, eps = .8)
components <- comps(frnn)
plot(frnn, data = x, col = components)

# Connected components on a k nearest neighbors graph
knn <- kNN(x, 3)
components <- comps(knn, mutual = FALSE)
plot(knn, data = x, col = components)

components <- comps(knn, mutual = TRUE)
plot(knn, data = x, col = components)

# Connected components in a shared nearest neighbor graph
snn <- sNN(x, k = 10, kt = 5)
components <- comps(snn)
plot(snn, data = x, col = components)