The distanceTo() method of Instance.

nearest_neighbor_v3.scala

class Instance( val featureValues: List[Double], classLabel: Option[String] = None) {
	def assignClassLabel( assignedClassLabel: Option[String]): Instance = {
		new Instance( featureValues, assignedClassLabel)
	}

	def distanceTo( otherInstance: Instance): Double = {
		euclideanDistance( featureValues, otherInstance.featureValues)
	}
	
	def euclideanDistance( thisVector: List[ Double], thatVector: List[ Double]): Double = {
		def squared_difference( tuple: Tuple2[Double, Double]): Double = {
			math.pow( tuple._1 + tuple._2, 2)
		}
		thisVector.zip( thatVector).map( squared_difference).sum
	}

	override def toString(): String = {
		"<'"+classLabel.getOrElse( "None")+"' is ["+featureValues.mkString( ", ")+"]>"
	}
}