feat: adds KNN Regressor

src/lib.rs

@@ -36,14 +36,14 @@
 //!
 //! Each category is assigned to a separate module.
 //!
-//! For example, KNN classifier is defined in [smartcore::neighbors::knn](neighbors/knn/index.html). To train and run it using standard Rust vectors you will
+//! For example, KNN classifier is defined in [smartcore::neighbors::knn_classifier](neighbors/knn_classifier/index.html). To train and run it using standard Rust vectors you will
 //! run this code:
 //!
 //! ```
 //! // DenseMatrix defenition
 //! use smartcore::linalg::naive::dense_matrix::*;
 //! // KNNClassifier
-//! use smartcore::neighbors::knn::*;
+//! use smartcore::neighbors::knn_classifier::*;
 //! // Various distance metrics
 //! use smartcore::math::distance::*;
 //!

src/neighbors/knn_classifier.rs

@@ -1,17 +1,10 @@
 use serde::{Deserialize, Serialize};
 
-use crate::algorithm::neighbour::cover_tree::CoverTree;
-use crate::algorithm::neighbour::linear_search::LinearKNNSearch;
+use crate::neighbors::{KNNAlgorithmName, KNNAlgorithm};
 use crate::linalg::{row_iter, Matrix};
 use crate::math::distance::Distance;
 use crate::math::num::FloatExt;
 
-#[derive(Serialize, Deserialize, Debug)]
-pub enum KNNAlgorithmName {
-    LinearSearch,
-    CoverTree,
-}
-
 #[derive(Serialize, Deserialize, Debug)]
 pub struct KNNClassifierParameters {
     pub algorithm: KNNAlgorithmName,
@@ -26,12 +19,6 @@ pub struct KNNClassifier<T: FloatExt, D: Distance<Vec<T>, T>> {
     k: usize,
 }
 
-#[derive(Serialize, Deserialize, Debug)]
-enum KNNAlgorithm<T: FloatExt, D: Distance<Vec<T>, T>> {
-    LinearSearch(LinearKNNSearch<Vec<T>, T, D>),
-    CoverTree(CoverTree<Vec<T>, T, D>),
-}
-
 impl Default for KNNClassifierParameters {
     fn default() -> Self {
         KNNClassifierParameters {
@@ -41,30 +28,6 @@ impl Default for KNNClassifierParameters {
     }
 }
 
-impl KNNAlgorithmName {
-    fn fit<T: FloatExt, D: Distance<Vec<T>, T>>(
-        &self,
-        data: Vec<Vec<T>>,
-        distance: D,
-    ) -> KNNAlgorithm<T, D> {
-        match *self {
-            KNNAlgorithmName::LinearSearch => {
-                KNNAlgorithm::LinearSearch(LinearKNNSearch::new(data, distance))
-            }
-            KNNAlgorithmName::CoverTree => KNNAlgorithm::CoverTree(CoverTree::new(data, distance)),
-        }
-    }
-}
-
-impl<T: FloatExt, D: Distance<Vec<T>, T>> KNNAlgorithm<T, D> {
-    fn find(&self, from: &Vec<T>, k: usize) -> Vec<usize> {
-        match *self {
-            KNNAlgorithm::LinearSearch(ref linear) => linear.find(from, k),
-            KNNAlgorithm::CoverTree(ref cover) => cover.find(from, k),
-        }
-    }
-}
-
 impl<T: FloatExt, D: Distance<Vec<T>, T>> PartialEq for KNNClassifier<T, D> {
     fn eq(&self, other: &Self) -> bool {
         if self.classes.len() != other.classes.len()

src/neighbors/knn_regressor.rs

@@ -0,0 +1,139 @@
+use serde::{Deserialize, Serialize};
+
+use crate::neighbors::{KNNAlgorithmName, KNNAlgorithm};
+use crate::linalg::{row_iter, BaseVector, Matrix};
+use crate::math::distance::Distance;
+use crate::math::num::FloatExt;
+
+
+#[derive(Serialize, Deserialize, Debug)]
+pub struct KNNRegressorParameters {
+    pub algorithm: KNNAlgorithmName,
+    pub k: usize,
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+pub struct KNNRegressor<T: FloatExt, D: Distance<Vec<T>, T>> {    
+    y: Vec<T>,
+    knn_algorithm: KNNAlgorithm<T, D>,
+    k: usize,
+}
+
+impl Default for KNNRegressorParameters {
+    fn default() -> Self {
+        KNNRegressorParameters {
+            algorithm: KNNAlgorithmName::CoverTree,
+            k: 3,
+        }
+    }
+}
+
+impl<T: FloatExt, D: Distance<Vec<T>, T>> PartialEq for KNNRegressor<T, D> {
+    fn eq(&self, other: &Self) -> bool {
+        if self.k != other.k || self.y.len() != other.y.len(){
+            return false;
+        } else {
+            for i in 0..self.y.len() {
+                if (self.y[i] - other.y[i]).abs() > T::epsilon() {
+                    return false;
+                }
+            }
+            true
+        }
+    }
+}
+
+impl<T: FloatExt, D: Distance<Vec<T>, T>> KNNRegressor<T, D> {
+    pub fn fit<M: Matrix<T>>(
+        x: &M,
+        y: &M::RowVector,
+        distance: D,
+        parameters: KNNRegressorParameters,
+    ) -> KNNRegressor<T, D> {
+        let y_m = M::from_row_vector(y.clone());
+
+        let (_, y_n) = y_m.shape();
+        let (x_n, _) = x.shape();
+
+        let data = row_iter(x).collect();
+        
+        assert!(
+            x_n == y_n,
+            format!(
+                "Size of x should equal size of y; |x|=[{}], |y|=[{}]",
+                x_n, y_n
+            )
+        );
+
+        assert!(
+            parameters.k > 1,
+            format!("k should be > 1, k=[{}]", parameters.k)
+        );        
+
+        KNNRegressor {            
+            y: y.to_vec(),
+            k: parameters.k,
+            knn_algorithm: parameters.algorithm.fit(data, distance),
+        }
+    }
+
+    pub fn predict<M: Matrix<T>>(&self, x: &M) -> M::RowVector {
+        let mut result = M::zeros(1, x.shape().0);
+
+        row_iter(x)
+            .enumerate()
+            .for_each(|(i, x)| result.set(0, i, self.predict_for_row(x)));
+
+        result.to_row_vector()
+    }
+
+    fn predict_for_row(&self, x: Vec<T>) -> T {
+        let idxs = self.knn_algorithm.find(&x, self.k);        
+        let mut result = T::zero();
+        for i in idxs {
+            result = result + self.y[i];            
+        }
+
+        result / T::from_usize(self.k).unwrap()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::linalg::naive::dense_matrix::DenseMatrix;
+    use crate::math::distance::Distances;
+
+    #[test]
+    fn knn_fit_predict() {
+        let x = DenseMatrix::from_array(&[&[1., 2.], &[3., 4.], &[5., 6.], &[7., 8.], &[9., 10.]]);
+        let y: Vec<f64> = vec![1., 2., 3., 4., 5.];
+        let y_exp = vec![2., 2., 3., 4., 4.];
+        let knn = KNNRegressor::fit(
+            &x,
+            &y,
+            Distances::euclidian(),
+            KNNRegressorParameters {
+                k: 3,
+                algorithm: KNNAlgorithmName::LinearSearch,
+            },
+        );
+        let y_hat = knn.predict(&x);
+        assert_eq!(5, Vec::len(&y_hat));
+        for i in 0..y_hat.len() {
+            assert!((y_hat[i] - y_exp[i]).abs() < std::f64::EPSILON);
+        }
+    }
+
+    #[test]
+    fn serde() {
+        let x = DenseMatrix::from_array(&[&[1., 2.], &[3., 4.], &[5., 6.], &[7., 8.], &[9., 10.]]);
+        let y = vec![1., 2., 3., 4., 5.];
+
+        let knn = KNNRegressor::fit(&x, &y, Distances::euclidian(), Default::default());
+
+        let deserialized_knn = bincode::deserialize(&bincode::serialize(&knn).unwrap()).unwrap();
+
+        assert_eq!(knn, deserialized_knn);
+    }
+}

src/neighbors/mod.rs

@@ -1 +1,47 @@
-pub mod knn;
+//! # Nearest Neighbors
+
+use serde::{Deserialize, Serialize};
+use crate::algorithm::neighbour::cover_tree::CoverTree;
+use crate::algorithm::neighbour::linear_search::LinearKNNSearch;
+use crate::math::distance::Distance;
+use crate::math::num::FloatExt;
+
+/// 
+pub mod knn_classifier;
+pub mod knn_regressor;
+
+#[derive(Serialize, Deserialize, Debug)]
+pub enum KNNAlgorithmName {
+    LinearSearch,
+    CoverTree,
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+enum KNNAlgorithm<T: FloatExt, D: Distance<Vec<T>, T>> {
+    LinearSearch(LinearKNNSearch<Vec<T>, T, D>),
+    CoverTree(CoverTree<Vec<T>, T, D>),
+}
+
+impl KNNAlgorithmName {
+    fn fit<T: FloatExt, D: Distance<Vec<T>, T>>(
+        &self,
+        data: Vec<Vec<T>>,
+        distance: D,
+    ) -> KNNAlgorithm<T, D> {
+        match *self {
+            KNNAlgorithmName::LinearSearch => {
+                KNNAlgorithm::LinearSearch(LinearKNNSearch::new(data, distance))
+            }
+            KNNAlgorithmName::CoverTree => KNNAlgorithm::CoverTree(CoverTree::new(data, distance)),
+        }
+    }
+}
+
+impl<T: FloatExt, D: Distance<Vec<T>, T>> KNNAlgorithm<T, D> {
+    fn find(&self, from: &Vec<T>, k: usize) -> Vec<usize> {
+        match *self {
+            KNNAlgorithm::LinearSearch(ref linear) => linear.find(from, k),
+            KNNAlgorithm::CoverTree(ref cover) => cover.find(from, k),
+        }
+    }
+}