Machine Learning with Swift

Update step

After the initial choice of centroids, we need to iterate over data points and update information about cluster assignment according to the distance to the closest centroid:

for (pointIndex, point) in data.enumerated() { 
  var minDistance = Double.infinity 
  for (clusterID, centroid) in centroids.enumerated() { 
    let distance = pow(distanceMetric(point, centroid), 2) 

Remember the newly calculated distance if it is less than the previously saved minimum distance for the corresponding data point:

    if minDistance > distance { 
      clusters[pointIndex] = clusterID 
      minDistance = distance 
    } 
  } 

Save information about WCSS for the future:

  WCSS += minDistance 
}