Add repeat_rows method to Matrix and corresponding unit test

src/matrix/mat.rs

@@ -327,6 +327,21 @@ impl<T: Clone> Matrix<T> {
         self.data = new_data;
         self.rows = new_rows;
     }
+
+    /// Return a new matrix where row 0 of `self` is repeated `n` times.
+    pub fn repeat_rows(&self, n: usize) -> Matrix<T>
+    where
+        T: Clone,
+    {
+        let mut data = Vec::with_capacity(n * self.cols());
+        let zeroth_row = self.row(0);
+        for value in &zeroth_row {
+            for _ in 0..n {
+                data.push(value.clone()); // Clone each element
+            }
+        }
+        Matrix::from_vec(data, n, self.cols)
+    }
 }
 
 impl Matrix<f64> {
@@ -1158,13 +1173,24 @@ mod tests {
     }
 
     #[test]
-    fn test_shape(){
+    fn test_shape() {
         let ma = static_test_matrix_2x4();
         assert_eq!(ma.shape(), (2, 4));
         assert_eq!(ma.rows(), 2);
         assert_eq!(ma.cols(), 4);
     }
 
+    #[test]
+    fn test_repeat_rows() {
+        let ma = static_test_matrix();
+        // Returns a new matrix where row 0 of `self` is repeated `n` times.
+        let repeated = ma.repeat_rows(3);
+        // assert all rows are equal to the first row
+        for r in 0..repeated.rows() {
+            assert_eq!(repeated.row(r), ma.row(0));
+        }
+    }
+
     #[test]
     #[should_panic(expected = "row index 3 out of bounds for 3 rows")]
     fn test_row_out_of_bounds() {