Calculate distances between units in a SOM

Description

Calculate distances between units in a SOM.

Usage

unit.distances(grid, toroidal)

Arguments

Value

Returns a (symmetrical) matrix containing distances. When grid$n.hood equals "circular", Euclidean distances are used; for grid$n.hood is "square" maximum distances. If toroidal equals TRUE, maps are joined at the edges and distances are calculated for the shortest path.

Author(s)

Ron Wehrens

Examples

library(kohonen)
data(wines)

kohmap <- som(wines, grid = somgrid(5, 5, "hexagonal"), rlen=10)

dists <- unit.distances(kohmap$grid, toroidal=FALSE)
plot(kohmap, type="property", property=dists[1,],
     main="Distances to unit 1", zlim=c(0,6),
     palette = rainbow, ncolors = 7, contin = TRUE)
dists <- unit.distances(kohmap$grid, toroidal=TRUE)
plot(kohmap, type="property", property=dists[1,],
     main="Distances to unit 1 (toroidal)", zlim=c(0,6),
     palette = rainbow, ncolors = 7, contin = TRUE)

kohmap <- som(wines, grid = somgrid(5, 5), rlen=10)

dists <- unit.distances(kohmap$grid, toroidal=FALSE)
plot(kohmap, type="property", property=dists[1,],
     main="Distances to unit 1", zlim=c(0,4),
     palette = rainbow, ncolors = 5, contin = TRUE)
dists <- unit.distances(kohmap$grid, toroidal=TRUE)
plot(kohmap, type="property", property=dists[1,],
     main="Distances to unit 1 (toroidal)", zlim=c(0,4),
     palette = rainbow, ncolors = 5, contin = TRUE)

Results