diff --git a/lib/xmet/series.py b/lib/xmet/series.py
index 48cc8ec..64ac90a 100644
--- a/lib/xmet/series.py
+++ b/lib/xmet/series.py
@@ -21,9 +21,12 @@ class Series(dict):
     def __init__(self):
         super().__init__()
 
+    def neighbors(self, series: Self):
+        return nearest(sorted(self.keys(),   reverse=True),
+                       sorted(series.keys(), reverse=True))
+
     def intersect(self, series: Self, intersection: SeriesIntersection, start: float=None) -> tuple[float]:
-        pairs = nearest(sorted(self.keys(),   reverse=True),
-                        sorted(series.keys(), reverse=True))
+        pairs = self.neighbors(series)
 
         for pair in pairs:
             v1, v2 = self[pair[0]], series[pair[1]]