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
p
is set to 1, it corresponds to the Manhattan distance (L1 norm). Whenp
is 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,
p
parameter 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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