GridGain Developers Hub
GitHub logo GridGain iso GridGain.com
GridGain Software Documentation

k-NN Regression

The Apache Ignite Machine Learning component provides two versions of the widely used k-NN (k-nearest neighbors) algorithm - one for classification tasks and the other for regression tasks.

This documentation reviews k-NN as a solution for the regression tasks.

Model description

The k-NN algorithm is a non-parametric method whose input consists of the k-closest training examples in the feature space. Each training example has a property value in a numerical form associated with the given training example.

The k-NN algorithm uses all training sets to predict a property value for the given test sample. This predicted property value is an average of the values of its k nearest neighbors. If k is 1, then the test sample is simply assigned to the property value of a single nearest neighbor.

Presently, Ignite supports a few parameters for the k-NN regression algorithm:

  • k - a number of nearest neighbors.

  • distanceMeasure - one of the distance metrics provided by the ML framework such as Euclidean, Hamming, or Manhattan.

  • KNNStrategy - could be SIMPLE or WEIGHTED (it enables a weighted k-NN algorithm),

  • datasetBuilder - helps to get access to the training set of objects for which the class is already known.

// Create trainer
KNNRegressionTrainer trainer = new KNNRegressionTrainer();

// Train model.
KNNRegressionModel knnMdl = (KNNRegressionModel) trainer.fit(
      datasetBuilder,
      (k, v) -> Arrays.copyOfRange(v, 1, v.length),
      (k, v) -> v[0])
  .withK(5)
  .withDistanceMeasure(new ManhattanDistance())
  .withStrategy(KNNStrategy.WEIGHTED);

// Make a prediction.
double prediction = knnMdl.apply(vectorizedData);

Example

To see how the k-NN regression can be used in practice, try this example, available on GitHub and delivered with the distribution package.

The training dataset is the Computer Hardware Data Set which can be loaded from the UCI Machine Learning Repository.