linearly decaying neighbourhood update function with
k = 2 is as good as the squared decay and the complex
Gaussian function with k = - 0.125. This form of update
function is very appropriate for use in conjunction with
Eqs. 12–14 since it is equivalent to increasing the number
of right shift time of the denominator term in both equations.
For a neighbour whose index is j far away from the
winner neuron, only the denominator term of Eq. 11 needs
to be updated. This changes the form of the denominator
term in Eq. 13 to be: