NAME

AI::NeuralNet::Kohonen::Node - a node for AI::NeuralNet::Kohonen

DESCRIPTION

Implimentation of a node in a SOM - see AI::NeuralNet::Kohonen.

CONSTRUCTOR (new)

Returns a new Node object. If no wieghts are supplied, the node's weights are randomized with real nubmers.

dim

The number of dimensions of this node's weights. Do not supply if you are supplying weight.

weight

Optional: a reference to an array containing the weight for this node. Supplying this allows the constructor to work out dim, above.

values

The values of the vector. Use x for unknown values.

missing_mask

Used to donate missing input in the node. Default is x.

METHOD distance_from

Find the distance of this node from the target.

Accepts: the target vector as an array reference.

Returns: the distance.

                       __________________
                      / i=n            2
        Distance  =  /   E  ( V  -  W )
                   \/   i=0    i     i

Where V is the current input vector, and W is this node's weight vector.

METHOD distance_effect

Calculates the effect on learning of distance from a given point (intended to be the BMU).

Accepts: the distance of this node from the given point; the radius of the neighbourhood of affect around the given point.

Returns:

                       (            2  )
                       (    distance   )
        THETA(t) = exp ( - ----------- )
                       (          2    )
                       (   2 sigma (t) )

Where distance is the distance of the node from the BMU, and sigma is the width of the neighbourhood as calculated elsewhere (see "FINDING THE NEIGHBOURS OF THE BMU" in AI::NeuralNet::Kohonen). THETA also decays over time.

The time t is always that of the calling object, and is not referenced here.

SEE ALSO

The AI::NeuralNet::Kohonen.

AUTHOR AND COYRIGHT

This implimentation Copyright (C) Lee Goddard, 2003. All Rights Reserved.

Available under the same terms as Perl itself.