Add intersection function, fixes #378

movingpandas/tests/test_trajectory_collection.py

@@ -161,6 +161,17 @@ def test_get_intersecting(self):
         assert len(collection) == 1
         assert collection.trajectories[0] == self.collection.trajectories[0]
 
+    def test_intersection(self):
+        feature = {
+            "geometry": {
+                "type": "Polygon",
+                "coordinates": [[(-1, -1), (-1, 1), (1, 1), (1, -1), (-1, -1)]],
+            },
+            "properties": {"id": 1, "name": "foo"},
+        }
+        collection = self.collection.intersection(feature)
+        assert len(collection) == 1
+
     def test_clip(self):
         polygon = Polygon([(-1, -1), (-1, 1), (1, 1), (1, -1), (-1, -1)])
         collection = self.collection.copy()
@@ -169,14 +180,16 @@ def test_clip(self):
         assert collection.trajectories[0].to_linestring().wkt == "LINESTRING (0 0, 1 0)"
 
     def test_clip_with_multipolygon(self):
-        polygon = MultiPolygon([
-            Polygon([(-1, -1), (-1, 1), (1, 1), (1, -1), (-1, -1)]),
-            Polygon([(5, 1), (7, 1), (7, 3), (5, 3), (5, 1)])
-        ])
+        polygon = MultiPolygon(
+            [
+                Polygon([(-1, -1), (-1, 1), (1, 1), (1, -1), (-1, -1)]),
+                Polygon([(5, 1), (7, 1), (7, 3), (5, 3), (5, 1)]),
+            ]
+        )
         collection = self.collection.clip(polygon)
         assert len(collection) == 2
         assert collection.trajectories[0].to_linestring().wkt == "LINESTRING (0 0, 1 0)"
-        assert collection.trajectories[1].to_linestring().wkt == "LINESTRING (6 1, 6 3)" 
+        assert collection.trajectories[1].to_linestring().wkt == "LINESTRING (6 1, 6 3)"
 
     """ Fails, related to https://github.com/movingpandas/movingpandas/discussions/235
     def test_clip_with_multipolygon2(self):
@@ -188,7 +201,7 @@ def test_clip_with_multipolygon2(self):
         assert len(collection) == 2
         assert collection.trajectories[0].to_linestring().wkt == "LINESTRING (0 0, 1 0)"
         assert collection.trajectories[1].to_linestring().wkt == "LINESTRING (3 0, 4 0)"
-    """ 
+    """
 
     def test_clip_with_min_length(self):
         polygon = Polygon([(-1, -1), (-1, 1), (1, 1), (1, -1), (-1, -1)])

movingpandas/trajectory.py

@@ -1433,7 +1433,7 @@ def clip(self, polygon, point_based=False):
 
     def intersection(self, feature, point_based=False):
         """
-        Return the trajectory segments that intersects the given feature.
+        Return the trajectory segments that intersects the given polygon feature.
 
         Feature attributes are appended to the trajectory's DataFrame.
 

movingpandas/trajectory_collection.py

@@ -55,8 +55,8 @@ def __init__(
         crs : string
             CRS of the x/y coordinates
         min_length : numeric
-            Desired minimum length of trajectories. Length is calculated using 
-            CRS units, except if the CRS is geographic (e.g. EPSG:4326 WGS84) 
+            Desired minimum length of trajectories. Length is calculated using
+            CRS units, except if the CRS is geographic (e.g. EPSG:4326 WGS84)
             then length is calculated in meters.
             (Shorter trajectories are discarded.)
         min_duration : timedelta
@@ -420,6 +420,42 @@ def get_intersecting(self, polygon):
         result.trajectories = intersecting
         return result
 
+    def intersection(self, feature, point_based=False):
+        """
+        Intersect trajectories with the given polygon feature.
+
+        Feature attributes are appended to the trajectory's DataFrame.
+
+        By default, the trajectory's line representation is clipped by the
+        polygon. If pointbased=True, the trajectory's point representation is
+        used instead, leading to shorter segments.
+
+        Parameters
+        ----------
+        feature : shapely Feature
+            Feature to intersect with
+        point_based : bool
+            Clipping method
+
+        Returns
+        -------
+        TrajectoryCollection
+            Intersecting trajectory segments
+        """
+        intersections = []
+        for traj in self:
+            try:
+                for intersect in traj.intersection(feature, point_based):
+                    if (
+                        intersect.get_length() >= self.min_length
+                    ):  # TODO also test min_duration
+                        intersections.append(intersect)
+            except:  # noqa E722
+                pass
+        result = copy(self)
+        result.trajectories = intersections
+        return result
+
     def clip(self, polygon, point_based=False):
         """
         Clip trajectories by the given polygon.
@@ -440,7 +476,9 @@ def clip(self, polygon, point_based=False):
         for traj in self:
             try:
                 for intersect in traj.clip(polygon, point_based):
-                    if (intersect.get_length() >= self.min_length):  # TODO also test min_duration
+                    if (
+                        intersect.get_length() >= self.min_length
+                    ):  # TODO also test min_duration
                         clipped.append(intersect)
             except:  # noqa E722
                 pass

tutorials/0-debug.ipynb

@@ -183,6 +183,47 @@
     "generalized.hvplot(tiles=None, c='speed', clim=(0,20), line_width=2, marker_size=0, **hv_defaults)"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "feature = {\n",
+    "    \"geometry\": {\n",
+    "        \"type\": \"Polygon\",\n",
+    "        \"coordinates\": [[(116, 39), (116.5, 39), (116.5, 40), (116, 40), (116, 39)]],\n",
+    "    },\n",
+    "    \"properties\": {\"id\": 1, \"name\": \"foo\"},\n",
+    "}"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "intersections = generalized.intersection(feature)\n",
+    "intersections.hvplot(tiles=None, c='speed', clim=(0,20), line_width=2, marker_size=0, **hv_defaults)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "intersections.trajectories[0].df"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
   {
    "cell_type": "code",
    "execution_count": null,
@@ -207,7 +248,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.10.10"
+   "version": "3.10.11"
   },
   "vscode": {
    "interpreter": {