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*k*-nearest neighbor classification

`ClassificationKNN`

is a nearest-neighbor classification model
in which you can alter both the distance metric and the number of nearest neighbors.
Because a `ClassificationKNN`

classifier stores training data, you can
use the model to compute resubstitution predictions. Alternatively, use the model to
classify new observations using the `predict`

method.

Create a `ClassificationKNN`

model using `fitcknn`

.

`compareHoldout` | Compare accuracies of two classification models using new data |

`crossval` | Cross-validate machine learning model |

`edge` | Edge of k-nearest neighbor classifier |

`gather` | Gather properties of machine learning model from GPU |

`lime` | Local interpretable model-agnostic explanations (LIME) |

`loss` | Loss of k-nearest neighbor classifier |

`margin` | Margin of k-nearest neighbor classifier |

`partialDependence` | Compute partial dependence |

`plotPartialDependence` | Create partial dependence plot (PDP) and individual conditional expectation (ICE) plots |

`predict` | Predict labels using k-nearest neighbor classification
model |

`resubEdge` | Resubstitution classification edge |

`resubLoss` | Resubstitution classification loss |

`resubMargin` | Resubstitution classification margin |

`resubPredict` | Classify training data using trained classifier |

`shapley` | Shapley values |

`testckfold` | Compare accuracies of two classification models by repeated cross-validation |

The

`compact`

function reduces the size of most classification models by removing the training data properties and any other properties that are not required to predict the labels of new observations. Because*k*-nearest neighbor classification models require all of the training data to predict labels, you cannot reduce the size of a`ClassificationKNN`

model.

`knnsearch`

finds the
*k*-nearest neighbors of points. `rangesearch`

finds all the points within a fixed distance. You can use
these functions for classification, as shown in Classify Query Data. If you want to perform
classification, then using `ClassificationKNN`

models can be more
convenient because you can train a classifier in one step (using `fitcknn`

) and classify in other steps (using `predict`

). Alternatively, you can train a *k*-nearest
neighbor classification model using one of the cross-validation options in the call to
`fitcknn`

. In this case, `fitcknn`

returns a
`ClassificationPartitionedModel`

cross-validated model object.