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Activation Rule

• The Self Organizing Map is called a competitive algorithm because units compete to represent the input pattern.

• At any one time only one of the output units is on (set to one) and all other units are off (set to zero).

• The algorithm chooses the winning unit by comparing the current input pattern against the weight vector of each of the output units. The one that is closest wins. That is, unit i wins if:

  |w_i - p| < |w_j - p| for all j

  where w_j is the weight vector of the jth unit and p is the current input vector.