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module OpenTox
module Algorithm
class Classification
# Classification with majority vote from neighbors weighted by similarity
# @param [Hash] params Keys `:activities, :sims, :value_map` are required
# @return [Numeric] A prediction value.
def self.weighted_majority_vote(neighbors)
return {:prediction => nil, :confidence => nil} if neighbors.empty?
neighbor_contribution = 0.0
confidence_sum = 0.0
confidence = 0.0
prediction = nil
$logger.debug "Weighted Majority Vote Classification."
values = neighbors.collect{|n| n[1]}.uniq
neighbors.each do |neighbor|
neighbor_weight = neighbor[2]
activity = values.index(neighbor[1]) + 1 # map values to integers > 1
neighbor_contribution += activity * neighbor_weight
if values.size == 2 # AM: provide compat to binary classification: 1=>false 2=>true
case activity
when 1
confidence_sum -= neighbor_weight
when 2
confidence_sum += neighbor_weight
end
else
confidence_sum += neighbor_weight
end
end
if values.size == 2
if confidence_sum >= 0.0
prediction = values[1]
elsif confidence_sum < 0.0
prediction = values[0]
end
else
prediction = (neighbor_contribution/confidence_sum).round # AM: new multinomial prediction
end
$logger.debug "Prediction: '" + prediction.to_s + "'." unless prediction.nil?
confidence = (confidence_sum/neighbors.size).abs
$logger.debug "Confidence: '" + confidence.to_s + "'." unless prediction.nil?
return {:prediction => prediction, :confidence => confidence.abs}
end
end
end
end
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