fix issue with slice_n_points on integer indexes (#1482)

darts/tests/test_timeseries.py

@@ -336,6 +336,14 @@ def helper_test_slice(test_case, test_series: TimeSeries):
         test_case.assertEqual(seriesG.start_time(), pd.Timestamp("20130101"))
         test_case.assertEqual(seriesG.end_time(), pd.Timestamp("20130107"))
 
+        # test slice_n_points_after and slice_n_points_before with integer-indexed series
+        s = TimeSeries.from_times_and_values(pd.RangeIndex(6, 10), np.arange(16, 20))
+        sliced_idx = s.slice_n_points_after(7, 2).time_index
+        test_case.assertTrue(all(sliced_idx == pd.RangeIndex(7, 9)))
+
+        sliced_idx = s.slice_n_points_before(8, 2).time_index
+        test_case.assertTrue(all(sliced_idx == pd.RangeIndex(7, 9)))
+
         # integer indexed series, step = 1, timestamps not in series
         values = np.random.rand(30)
         idx = pd.RangeIndex(start=0, stop=30, step=1)

darts/timeseries.py

@@ -2272,7 +2272,7 @@ def slice_n_points_after(
         self._raise_if_not_within(start_ts)
 
         if isinstance(start_ts, (int, np.int64)):
-            return self[start_ts : start_ts + n]
+            return self[pd.RangeIndex(start=start_ts, stop=start_ts + n)]
         elif isinstance(start_ts, pd.Timestamp):
             # get first timestamp greater or equal to start_ts
             tss = self._get_first_timestamp_after(start_ts)
@@ -2308,7 +2308,7 @@ def slice_n_points_before(
         self._raise_if_not_within(end_ts)
 
         if isinstance(end_ts, (int, np.int64)):
-            return self[end_ts - n + 1 : end_ts + 1]
+            return self[pd.RangeIndex(start=end_ts - n + 1, stop=end_ts + 1)]
         elif isinstance(end_ts, pd.Timestamp):
             # get last timestamp smaller or equal to start_ts
             tss = self._get_last_timestamp_before(end_ts)