feat: adds FitFailedError and PredictFailedError

Author: Volodymyr Orlov

src/cluster/kmeans.rs

@@ -43,8 +43,8 @@
 //!            &[5.2, 2.7, 3.9, 1.4],
 //!            ]);
 //!
-//! let kmeans = KMeans::new(&x, 2, Default::default()); // Fit to data, 2 clusters
-//! let y_hat = kmeans.predict(&x); // use the same points for prediction
+//! let kmeans = KMeans::fit(&x, 2, Default::default()).unwrap(); // Fit to data, 2 clusters
+//! let y_hat = kmeans.predict(&x).unwrap(); // use the same points for prediction
 //! ```
 //!
 //! ## References:
@@ -60,6 +60,7 @@ use std::iter::Sum;
 
 use serde::{Deserialize, Serialize};
 
+use crate::error::{FitFailedError, PredictFailedError};
 use crate::algorithm::neighbour::bbd_tree::BBDTree;
 use crate::linalg::Matrix;
 use crate::math::distance::euclidian::*;
@@ -117,18 +118,17 @@ impl<T: RealNumber + Sum> KMeans<T> {
     /// * `data` - training instances to cluster
     /// * `k` - number of clusters
     /// * `parameters` - cluster parameters
-    pub fn new<M: Matrix<T>>(data: &M, k: usize, parameters: KMeansParameters) -> KMeans<T> {
+    pub fn fit<M: Matrix<T>>(data: &M, k: usize, parameters: KMeansParameters) -> Result<KMeans<T>, FitFailedError> {
         let bbd = BBDTree::new(data);
 
         if k < 2 {
-            panic!("Invalid number of clusters: {}", k);
+            return Err(FitFailedError::new(&format!("Invalid number of clusters: {}", k)));
         }
 
         if parameters.max_iter <= 0 {
-            panic!(
-                "Invalid maximum number of iterations: {}",
+            return Err(FitFailedError::new(&format!("Invalid maximum number of iterations: {}",
                 parameters.max_iter
-            );
+            )));
         }
 
         let (n, d) = data.shape();
@@ -172,18 +172,18 @@ impl<T: RealNumber + Sum> KMeans<T> {
             }
         }
 
-        KMeans {
+        Ok(KMeans {
             k: k,
             y: y,
             size: size,
             distortion: distortion,
             centroids: centroids,
-        }
+        })
     }
 
     /// Predict clusters for `x`
     /// * `x` - matrix with new data to transform of size _KxM_ , where _K_ is number of new samples and _M_ is number of features.
-    pub fn predict<M: Matrix<T>>(&self, x: &M) -> M::RowVector {
+    pub fn predict<M: Matrix<T>>(&self, x: &M) -> Result<M::RowVector, PredictFailedError> {
         let (n, _) = x.shape();
         let mut result = M::zeros(1, n);
 
@@ -201,7 +201,7 @@ impl<T: RealNumber + Sum> KMeans<T> {
             result.set(0, i, T::from(best_cluster).unwrap());
         }
 
-        result.to_row_vector()
+        Ok(result.to_row_vector())
     }
 
     fn kmeans_plus_plus<M: Matrix<T>>(data: &M, k: usize) -> Vec<usize> {
@@ -262,6 +262,20 @@ mod tests {
     use super::*;
     use crate::linalg::naive::dense_matrix::DenseMatrix;
 
+    #[test]
+    fn invalid_k() {
+        let x = DenseMatrix::from_2d_array(&[
+            &[1., 2., 3.],
+            &[4., 5., 6.],           
+        ]);
+
+        println!("{:?}", KMeans::fit(&x, 0, Default::default()));
+
+        assert!(KMeans::fit(&x, 0, Default::default()).is_err());                
+        assert_eq!("Invalid number of clusters: 1", KMeans::fit(&x, 1, Default::default()).unwrap_err().to_string());
+
+    }
+
     #[test]
     fn fit_predict_iris() {
         let x = DenseMatrix::from_2d_array(&[
@@ -287,9 +301,9 @@ mod tests {
             &[5.2, 2.7, 3.9, 1.4],
         ]);
 
-        let kmeans = KMeans::new(&x, 2, Default::default());
+        let kmeans = KMeans::fit(&x, 2, Default::default()).unwrap();
 
-        let y = kmeans.predict(&x);
+        let y = kmeans.predict(&x).unwrap();
 
         for i in 0..y.len() {
             assert_eq!(y[i] as usize, kmeans.y[i]);
@@ -321,7 +335,7 @@ mod tests {
             &[5.2, 2.7, 3.9, 1.4],
         ]);
 
-        let kmeans = KMeans::new(&x, 2, Default::default());
+        let kmeans = KMeans::fit(&x, 2, Default::default()).unwrap();
 
         let deserialized_kmeans: KMeans<f64> =
             serde_json::from_str(&serde_json::to_string(&kmeans).unwrap()).unwrap();

src/error/mod.rs

@@ -0,0 +1,55 @@
+//! # Custom warnings and errors
+use std::error::Error;
+use std::fmt;
+
+/// Error to be raised when model does not fits data.
+#[derive(Debug)]
+pub struct FitFailedError {
+    details: String
+}
+
+/// Error to be raised when model prediction cannot be calculated.
+#[derive(Debug)]
+pub struct PredictFailedError {
+    details: String
+}
+
+impl FitFailedError {
+    /// Creates new instance of `FitFailedError`
+    /// * `msg` - description of the error
+    pub fn new(msg: &str) -> FitFailedError {
+        FitFailedError{details: msg.to_string()}
+    }
+}
+
+impl fmt::Display for FitFailedError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f,"{}",self.details)
+    }
+}
+
+impl Error for FitFailedError {
+    fn description(&self) -> &str {
+        &self.details
+    }
+}
+
+impl PredictFailedError {
+    /// Creates new instance of `PredictFailedError`
+    /// * `msg` - description of the error
+    pub fn new(msg: &str) -> PredictFailedError {
+        PredictFailedError{details: msg.to_string()}
+    }
+}
+
+impl fmt::Display for PredictFailedError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f,"{}",self.details)
+    }
+}
+
+impl Error for PredictFailedError {
+    fn description(&self) -> &str {
+        &self.details
+    }
+}

src/lib.rs

@@ -89,3 +89,4 @@ pub mod neighbors;
 pub(crate) mod optimization;
 /// Supervised tree-based learning methods
 pub mod tree;
+pub mod error;