fix: ridge regression, code refactoring

src/linear/ridge_regression.rs

@@ -134,6 +134,10 @@ impl<T: RealNumber, M: Matrix<T>> RidgeRegression<T, M> {
             )));
         }
 
+        if y.len() != n {
+            return Err(Failed::fit(&format!("Number of rows in X should = len(y)")));
+        }
+
         let y_column = M::from_row_vector(y.clone()).transpose();
 
         let (w, b) = if parameters.normalize {
@@ -216,8 +220,8 @@ impl<T: RealNumber, M: Matrix<T>> RidgeRegression<T, M> {
     }
 
     /// Get estimates regression coefficients
-    pub fn coefficients(&self) -> M {
-        self.coefficients.clone()
+    pub fn coefficients(&self) -> &M {
+        &self.coefficients
     }
 
     /// Get estimate of intercept