fix getitem with rangeindex start != 0 and freq != 1 (#1868)

* fix getitem with rangeindex start != 0 and freq != 1

* update changelog

CHANGELOG.md

@@ -27,6 +27,7 @@ but cannot always guarantee backwards compatibility. Changes that may **break co
 - Fixed an issue with `TorchForecastingModel.load_from_checkpoint()` not properly loading the loss function and metrics. [#1749](https://github.com/unit8co/darts/pull/1749) by [Antoine Madrona](https://github.com/madtoinou).
 - Fixed a bug when loading the weights of a `TorchForecastingModel` trained with encoders or a Likelihood. [#1744](https://github.com/unit8co/darts/pull/1744) by [Antoine Madrona](https://github.com/madtoinou).
 - Fixed a bug when using selected `target_components` with `ShapExplainer. [#1803](https://github.com/unit8co/darts/pull/#1803) by [Dennis Bader](https://github.com/dennisbader).
+- Fixed `TimeSeries.__getitem__()` for series with a RangeIndex with start != 0 and freq != 1. [#1868](https://github.com/unit8co/darts/pull/#1868) by [Dennis Bader](https://github.com/dennisbader).
 
 **Removed**
 - Removed support for Python 3.7 [#1864](https://github.com/unit8co/darts/pull/#1864) by [Dennis Bader](https://github.com/dennisbader).

darts/tests/test_timeseries.py

@@ -867,7 +867,7 @@ def test_ops(self):
             # Cannot divide by 0.
             self.series1 / 0
 
-    def test_getitem(self):
+    def test_getitem_datetime_index(self):
         seriesA: TimeSeries = self.series1.drop_after(pd.Timestamp("20130105"))
         self.assertEqual(self.series1[pd.date_range("20130101", " 20130104")], seriesA)
         self.assertEqual(self.series1[:4], seriesA)
@@ -890,6 +890,50 @@ def test_getitem(self):
         with self.assertRaises(IndexError):
             self.series1[::-1]
 
+    def test_getitem_integer_index(self):
+        freq = 3
+        start = 1
+        end = start + (len(self.series1) - 1) * freq
+        idx_int = pd.RangeIndex(start=start, stop=end + freq, step=freq)
+        series = TimeSeries.from_times_and_values(
+            times=idx_int, values=self.series1.values()
+        )
+        assert series.freq == freq
+        assert series.start_time() == start
+        assert series.end_time() == end
+        assert series[idx_int] == series == series[0 : len(series)]
+
+        series_single = series.drop_after(start + 2 * freq)
+        assert (
+            series[pd.RangeIndex(start=start, stop=start + 2 * freq, step=freq)]
+            == series_single
+        )
+        assert series[:2] == series_single
+        assert series_single.freq == freq
+        assert series_single.start_time() == start
+        assert series_single.end_time() == start + freq
+
+        idx_single = pd.RangeIndex(start=start + freq, stop=start + 2 * freq, step=freq)
+        assert series[idx_single].time_index == idx_single
+        assert series[idx_single].pd_series().equals(series.pd_series()[1:2])
+        assert series[idx_single] == series[1:2] == series[1]
+
+        # cannot slice with two RangeIndex
+        with pytest.raises(IndexError):
+            _ = series[idx_single : idx_single + freq]
+
+        # RangeIndex not in time_index
+        with pytest.raises(KeyError):
+            _ = series[idx_single - 1]
+
+        # RangeIndex start is out of bounds
+        with pytest.raises(KeyError):
+            _ = series[pd.RangeIndex(start - freq, stop=end + freq, step=freq)]
+
+        # RangeIndex end is out of bounds
+        with pytest.raises(KeyError):
+            _ = series[pd.RangeIndex(start, stop=end + 2 * freq, step=freq)]
+
     def test_fill_missing_dates(self):
         with self.assertRaises(ValueError):
             # Series cannot have date holes without automatic filling

darts/timeseries.py

@@ -4916,7 +4916,9 @@ def _set_freq_in_xa(xa_: xr.DataArray):
                 xa_ = xa_.assign_coords(
                     {
                         self._time_dim: pd.RangeIndex(
-                            start=key, stop=key + self.freq, step=self.freq
+                            start=time_idx[0],
+                            stop=time_idx[0] + self.freq,
+                            step=self.freq,
                         )
                     }
                 )