Implement column renaming in DataFrame, updating both logical names and underlying Frame references.

Allow explicit setting range index

src/dataframe/df.rs

@@ -252,9 +252,28 @@ impl DataFrame {
                 old_name
             )
         });
-        self.data.insert(new_name.clone(), column);
+        let new_name_clone = new_name.clone();
+        self.data.insert(new_name, column);
         if let Some(pos) = self.column_names.iter().position(|n| n == old_name) {
-            self.column_names[pos] = new_name;
+            self.column_names[pos] = new_name_clone.clone();
+        }
+
+        // rename the column in the underlying Frame as well
+        if let Some(col) = self.data.get_mut(&new_name_clone) {
+            match col {
+                DataFrameColumn::F64(frame) => {
+                    frame.rename(old_name, new_name_clone.clone());
+                }
+                DataFrameColumn::I64(frame) => {
+                    frame.rename(old_name, new_name_clone.clone());
+                }
+                DataFrameColumn::String(frame) => {
+                    frame.rename(old_name, new_name_clone.clone());
+                }
+                DataFrameColumn::Bool(frame) => {
+                    frame.rename(old_name, new_name_clone.clone());
+                }
+            }
         }
     }
 

src/frame/base.rs

@@ -232,11 +232,18 @@ impl<T: Clone + PartialEq> Frame<T> {
                 }
                 (RowIndex::Date(vals), RowIndexLookup::Date(lookup))
             }
-            Some(RowIndex::Range(_)) => {
+            Some(RowIndex::Range(ref r)) => {
+                // If the length of the range does not match the number of rows, panic.
+                if r.end.saturating_sub(r.start) != num_rows {
                     panic!(
-                    "Frame::new: Cannot explicitly provide a Range index. Use None for default range."
+                        "Frame::new: Range index length ({}) mismatch matrix rows ({})",
+                        r.end.saturating_sub(r.start),
+                        num_rows
                     );
                 }
+                // return the range as is.
+                (RowIndex::Range(r.clone()), RowIndexLookup::None)
+            }
             None => {
                 // Default to a sequential range index.
                 (RowIndex::Range(0..num_rows), RowIndexLookup::None)
@@ -1129,10 +1136,10 @@ mod tests {
         Frame::new(matrix, vec!["X", "Y"], Some(index));
     }
     #[test]
-    #[should_panic(expected = "Cannot explicitly provide a Range index")]
-    fn frame_new_panic_explicit_range() {
-        let matrix = create_test_matrix_f64();
-        let index = RowIndex::Range(0..3); // User cannot provide Range directly
+    #[should_panic(expected = "Frame::new: Range index length (4) mismatch matrix rows (3)")]
+    fn frame_new_panic_invalid_explicit_range_index() {
+        let matrix = create_test_matrix_f64(); // 3 rows
+        let index = RowIndex::Range(0..4); // Range 0..4 but only 3 rows
         Frame::new(matrix, vec!["A", "B"], Some(index));
     }