K-Nearest Neighbors (KNN) is a simple yet effective classification and regression algorithm. While KNN doesn't have as many hyperparameters as some other algorithms, there are still some important parameters to consider:
n_neighbors:
- The number of neighbors to consider when making predictions. It's a crucial hyperparameter as it determines the granularity of decision boundaries. Smaller values may lead to overfitting, while larger values may result in underfitting.
weights:
- Specifies the weight assigned to each neighbor when making predictions. Common options are 'uniform' (all neighbors have equal weight) and 'distance' (closer neighbors have more influence).
p:
- The power parameter for the Minkowski distance metric. When
pis set to 1, it corresponds to the Manhattan distance (L1 norm). Whenpis set to 2, it corresponds to the Euclidean distance (L2 norm).
- The power parameter for the Minkowski distance metric. When
metric:
- The distance metric used to measure the distance between data points. Common options include 'euclidean', 'manhattan', 'chebyshev', 'minkowski', and more.
algorithm:
- The algorithm used to compute nearest neighbors. Common choices include 'auto' (automatically choose the most efficient algorithm), 'ball_tree', 'kd_tree', and 'brute-force' ('brute').
leaf_size:
- The size of the leaf node in the KD tree or Ball tree. It affects the speed of the nearest neighbor search.
n_jobs:
- The number of CPU cores to use for parallelism when computing neighbors. It can speed up the nearest neighbor search for large datasets.
metric_params:
- Additional parameters specific to the chosen distance metric. For example,
pparameter for Minkowski distance.
- Additional parameters specific to the chosen distance metric. For example,
algorithm-specific parameters:
- Some algorithms, like 'kd_tree' and 'ball_tree', have their own set of parameters that can be tuned for optimization.
The choice of these parameters depends on the specific problem and dataset. Experimentation and cross-validation are often used to find the best combination of parameter values that result in the highest model performance.
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