# unit.distances: SOM-grid related functions In kohonen: Supervised and Unsupervised Self-Organising Maps

## Description

Function `somgrid` (modified from the version in the class package) sets up a grid of units, of a specified size and topology. Distances between grid units are calculated by function `unit.distances`.

## Usage

 ```1 2 3``` ```somgrid(xdim = 8, ydim = 6, topo = c("rectangular", "hexagonal"), neighbourhood.fct = c("bubble", "gaussian"), toroidal = FALSE) unit.distances(grid, toroidal) ```

## Arguments

 `xdim, ydim` dimensions of the grid. `topo` choose between a hexagonal or rectangular topology. `neighbourhood.fct` choose between bubble and gaussian neighbourhoods when training a SOM. `toroidal` logical, whether the grid is toroidal or not. If not provided to the `unit.distances` function, the information in the `grid` object will be used. `grid` an object of class `somgrid`.

## Value

Function `somgrid` returns an object of class "somgrid", with elements `pts`, and the input arguments to the function.

Function `unit.distances` returns a (symmetrical) matrix containing distances. When `grid\$n.hood` equals "circular", Euclidean distances are used; for `grid\$n.hood` is "square" maximum distances. For toroidal maps (joined at the edges) distances are calculated for the shortest path.

Ron Wehrens

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14``` ```mygrid <- somgrid(5, 5, "hexagonal") fakesom <- list(grid = mygrid) class(fakesom) <- "kohonen" par(mfrow = c(2,1)) dists <- unit.distances(mygrid) plot(fakesom, type="property", property = dists[1,], main="Distances to unit 1", zlim=c(0,6), palette = rainbow, ncolors = 7) dists <- unit.distances(mygrid, toroidal=TRUE) plot(fakesom, type="property", property = dists[1,], main="Distances to unit 1 (toroidal)", zlim=c(0,6), palette = rainbow, ncolors = 7) ```

### Example output

```
```

kohonen documentation built on Aug. 29, 2017, 1:07 a.m.