A weighted Euclidean distance function implementation

gistfile1.scala

package breeze.linalg.functions

import breeze.generic.UFunc
import breeze.linalg.{SparseVector, DenseVector}
import breeze.numerics.sqrt

/**
 * A weighted Euclidean distance function implementation
 */
object weightedEuclideanDistance extends UFunc {

  implicit object weightedEuclideanFromDenseVector_DV_DV_DV_D
    extends Impl3[DenseVector[Double], DenseVector[Double], DenseVector[Double], Double] {

    override def apply(v: DenseVector[Double],
      v2: DenseVector[Double],
      weights: DenseVector[Double]): Double = {
      val d = v - v2
      sqrt(d dot (weights :* d))
    }
  }

  implicit object weightedEuclideanFromSparseVector_SV_SV_SV_D
    extends Impl3[SparseVector[Double], SparseVector[Double], SparseVector[Double], Double] {

    override def apply(v: SparseVector[Double],
      v2: SparseVector[Double],
      weights: SparseVector[Double]): Double = {
      val d = v - v2
      sqrt(d dot (weights :* d))
    }
  }
}