| 7 | |
| 8 | |
| 9 | class KNN: |
| 10 | def __init__( |
| 11 | self, k=5, leaf_size=40, classifier=True, metric=None, weights="uniform", |
| 12 | ): |
| 13 | """ |
| 14 | A `k`-nearest neighbors (kNN) model relying on a ball tree for efficient |
| 15 | computation. |
| 16 | |
| 17 | Parameters |
| 18 | ---------- |
| 19 | k : int |
| 20 | The number of neighbors to use during prediction. Default is 5. |
| 21 | leaf_size : int |
| 22 | The maximum number of datapoints at each leaf in the ball tree. |
| 23 | Default is 40. |
| 24 | classifier : bool |
| 25 | Whether to treat the values in Y as class labels (classifier = |
| 26 | True) or real-valued targets (classifier = False). Default is True. |
| 27 | metric : :doc:`Distance metric <numpy_ml.utils.distance_metrics>` or None |
| 28 | The distance metric to use for computing nearest neighbors. If |
| 29 | None, use the :func:`~numpy_ml.utils.distance_metrics.euclidean` |
| 30 | metric by default. Default is None. |
| 31 | weights : {'uniform', 'distance'} |
| 32 | How to weight the predictions from each neighbors. 'uniform' |
| 33 | assigns uniform weights to each neighbor, while 'distance' assigns |
| 34 | weights proportional to the inverse of the distance from the query |
| 35 | point. Default is 'uniform'. |
| 36 | """ |
| 37 | self._ball_tree = BallTree(leaf_size=leaf_size, metric=metric) |
| 38 | self.hyperparameters = { |
| 39 | "id": "KNN", |
| 40 | "k": k, |
| 41 | "leaf_size": leaf_size, |
| 42 | "classifier": classifier, |
| 43 | "metric": str(metric), |
| 44 | "weights": weights, |
| 45 | } |
| 46 | |
| 47 | def fit(self, X, y): |
| 48 | r""" |
| 49 | Fit the model to the data and targets in `X` and `y` |
| 50 | |
| 51 | Parameters |
| 52 | ---------- |
| 53 | X : numpy array of shape `(N, M)` |
| 54 | An array of `N` examples to generate predictions on. |
| 55 | y : numpy array of shape `(N, *)` |
| 56 | Targets for the `N` rows in `X`. |
| 57 | """ |
| 58 | if X.ndim != 2: |
| 59 | raise Exception("X must be two-dimensional") |
| 60 | self._ball_tree.fit(X, y) |
| 61 | |
| 62 | def predict(self, X): |
| 63 | r""" |
| 64 | Generate predictions for the targets associated with the rows in `X`. |
| 65 | |
| 66 | Parameters |
no outgoing calls