| SOM {class} | R Documentation |
Kohonen's Self-Organizing Maps are a crude form of multidimensional scaling.
SOM(data, grid = somgrid(), rlen = 10000, alpha, radii, init)
data |
a matrix or data frame of observations, scaled so that Euclidean distance is appropriate. |
grid |
A grid for the representatives: see somgrid.
|
rlen |
the number of updates: used only in the defaults for alpha and radii.
|
alpha |
the amount of change: one update is done for each element of alpha.
Default is to decline linearly from 0.05 to 0 over rlen updates.
|
radii |
the radii of the neighbourhood to be used for each update: must be the
same length as alpha. Default is to decline linearly from 4 to 1
over rlen updates.
|
init |
the initial representatives. If missing, chosen (without replacement)
randomly from data.
|
alpha and radii can also be lists, in which case each component is
used in turn, allowing two- or more phase training.
an object of class "SOM" with components
grid |
the grid, an object of class "somgrid".
|
codes |
a matrix of representatives. |
Kohonen, T. (1995) Self-Organizing Maps. Springer-Verlag
Kohonen, T., Hynninen, J., Kangas, J. and Laaksonen, J. (1996) SOM PAK: The self-organizing map program package. Laboratory of Computer and Information Science, Helsinki University of Technology, Technical Report A31.
Ripley, B. D. (1996) Pattern Recognition and Neural Networks. Cambridge.
Venables, W. N. and Ripley, B. D. (2002) Modern Applied Statistics with S. Fourth edition. Springer.
data(crabs, package = "MASS")
lcrabs <- log(crabs[, 4:8])
crabs.grp <- factor(c("B", "b", "O", "o")[rep(1:4, rep(50,4))])
gr <- somgrid(topo = "hexagonal")
crabs.som <- SOM(lcrabs, gr)
plot(crabs.som)
## 2-phase training
crabs.som2 <- SOM(lcrabs, gr,
alpha = list(seq(0.05, 0, len = 1e4), seq(0.02, 0, len = 1e5)),
radii = list(seq(8, 1, len = 1e4), seq(4, 1, len = 1e5)))
plot(crabs.som2)