Create nodes at lines intersections

src/snkit/network.py

@@ -300,7 +300,7 @@ def split_edges_at_intersections(network, tolerance=1e-9):
     split_edges = []
     split_points = []
     for edge in tqdm(
-        network.edges.itertuples(index=False), desc='split', total=len(network.edges)
+        network.edges.itertuples(index=False), desc="split", total=len(network.edges)
     ):
         # note: the symmetry of intersection is not exploited here.
         # (If A intersects B, then B intersects A)
@@ -315,28 +315,15 @@ def split_edges_at_intersections(network, tolerance=1e-9):
             # these are *new geometrical objects* not in the sindex
             # therefore they cannot be returned by internal _intersects*
             intersection = Point()
-            # restrict intersection to crossing
-            # this excludes self overlap and end-points intersections
-            # WARNING: how are self-crossing handled? (e.g. loop-like)
-            if edge.geometry.crosses(hit):
+            # excluding itself
+            # note that __eq__ is used on purpose instead of equals()
+            # this is stricter: for geometries constructed in the same way
+            # WARNING: this excludes sensical self-intersections, to be solved.
+            if edge != hit:
                 intersection = edge.geometry.intersection(hit)
 
-            # then keep track of the intersection points
-            geom_type = intersection.geom_type
-            if intersection.is_empty:
-                continue
-            elif geom_type == 'Point':
-                hits_points.append(intersection)
-            elif geom_type == 'MultiPoint':
-                for point in intersection.geoms:
-                    hits_points.append(point)
-            elif geom_type == 'MultiLineString':
-                # when lines almost overlap for a stretch
-                for line in intersection.geoms:
-                    start = Point(line.coords[0])
-                    end = Point(line.coords[-1])
-                    hits_points.append(start)
-                    hits_points.append(end)
+            # then extract the intersection points
+            hits_points = intersection_endpoints(intersection, hits_points)
 
         # store the split edges and intersection points
         split_points.extend(hits_points)
@@ -660,6 +647,36 @@ def line_endpoints(line):
     return start, end
 
 
+def intersection_endpoints(geom, output=[]):
+    """Return the points from an intersection geometry
+
+    It extracts the starting and ending points of intersection
+    geometries recursively and appends them to `output`.
+    This doesn't handle polygons or collections of polygons.
+    """
+    geom_type = geom.geom_type
+    if geom.is_empty:
+        pass
+    elif geom_type == "Point":
+        output.append(geom)
+    elif geom_type == "LineString":
+        start = Point(geom.coords[0])
+        end = Point(geom.coords[-1])
+        output.append(start)
+        output.append(end)
+    # recursively for collections of geometries
+    # note that there is no shared inheritance relationship
+    elif (
+        geom_type == "MultiPoint"
+        or geom_type == "MultiLineString"
+        or geom_type == "GeometryCollection"
+    ):
+        for geom_ in geom.geoms:
+            output = intersection_endpoints(geom_, output)
+
+    return output
+
+
 def split_edge_at_points(edge, points, tolerance=1e-9):
     """Split edge at point/multipoint"""
     try:
@@ -766,14 +783,20 @@ def to_networkx(network, directed=False, weight_col=None):
         G.add_nodes_from(network.nodes.id.to_list())
 
         # add nodal positions from geom
-        for node_id, x, y in zip(network.nodes.id, network.nodes.geometry.x, network.nodes.geometry.y):
+        for node_id, x, y in zip(
+            network.nodes.id, network.nodes.geometry.x, network.nodes.geometry.y
+        ):
             G.nodes[node_id]["pos"] = (x, y)
 
         # get edges from network data
         if weight_col is None:
             # default to geometry length
             edges_as_list = list(
-                zip(network.edges.from_id, network.edges.to_id, network.edges.geometry.length)
+                zip(
+                    network.edges.from_id,
+                    network.edges.to_id,
+                    network.edges.geometry.length,
+                )
             )
         else:
             edges_as_list = list(

tests/test_init.py

@@ -2,6 +2,7 @@
 """
 # pylint: disable=C0103
 import warnings
+from black import Line
 
 with warnings.catch_warnings():
     warnings.filterwarnings("ignore", category=DeprecationWarning)
@@ -183,6 +184,162 @@ def split_intersection():
     return snkit.Network(edges=edges, nodes=nodes)
 
 
+@fixture
+def unsplit_multiple_intersections():
+    """Multiple edges intersections, all edges unsplit
+       b   f
+       |   |
+    c--|---|--d
+       |   |
+       a   e
+    """
+    a = Point((1, 0))
+    b = Point((1, 2))
+    c = Point((0, 1))
+    d = Point((3, 1))
+    e = Point((2, 0))
+    f = Point((2, 2))
+    nodes = GeoDataFrame(data={"geometry": [a, b, c, d, e, f]})
+    ab = LineString([a, b])
+    cd = LineString([c, d])
+    ef = LineString([e, f])
+    edges = GeoDataFrame(data={"geometry": [ab, cd, ef]})
+    return snkit.Network(edges=edges, nodes=nodes)
+
+
+@fixture
+def split_multiple_intersections():
+    """Multiple edges intersections, all edges split
+       b   f
+       |   |
+    c--x---y--d
+       |   |
+       a   e
+    """
+    a = Point((1, 0))
+    b = Point((1, 2))
+    c = Point((0, 1))
+    d = Point((3, 1))
+    e = Point((2, 0))
+    f = Point((2, 2))
+    x = Point((1, 1))
+    y = Point((2, 1))
+    nodes = GeoDataFrame(data={"geometry": [a, b, c, d, e, f, x, y]})
+    ax = LineString([a, x])
+    xb = LineString([x, b])
+    cx = LineString([c, x])
+    xy = LineString([x, y])
+    yd = LineString([y, d])
+    ey = LineString([e, y])
+    yf = LineString([y, f])
+    edges = GeoDataFrame(data={"geometry": [ax, xb, cx, xy, yd, ey, yf]})
+    return snkit.Network(edges=edges, nodes=nodes)
+
+
+@fixture
+def unsplit_overlapping_lines():
+    """Overlapping lines for a section
+       c--d
+       ||
+    b--|
+       |
+       a
+    """
+    a = Point((1, 0))
+    b = Point((0, 1))
+    c = Point((1, 2))
+    d = Point((2, 2))
+    # x is just a construction point
+    x = Point((1, 1))
+    nodes = GeoDataFrame(data={"geometry": [a, b, c, d]})
+    ac = LineString([a, c])
+    bd = LineString([b, x, c, d])
+    edges = GeoDataFrame(data={"geometry": [ac, bd]})
+    return snkit.Network(edges=edges, nodes=nodes)
+
+
+@fixture
+def split_overlapping_lines():
+    """Split of overlapping lines for a section
+       c--d
+       ||
+    b--x
+       |
+       a
+    """
+    a = Point((1, 0))
+    b = Point((0, 1))
+    c = Point((1, 2))
+    d = Point((2, 2))
+    x = Point((1, 1))
+    nodes = GeoDataFrame(data={"geometry": [a, b, c, d, x]})
+    ax = LineString([a, x])
+    bx = LineString([b, x])
+    xc = LineString([x, c])
+    cd = LineString([c, d])
+    # note that there are two edges 'xc'
+    edges = GeoDataFrame(data={"geometry": [ax, xc, bx, xc, cd]})
+    return snkit.Network(edges=edges, nodes=nodes)
+
+
+@fixture
+def unsplit_heterogeneous_intersection():
+    """Crossing point and overlapping line
+       b--c
+       |  |
+    e--|--------f
+       |   --d
+       a
+
+       * --d overlaps with e-f
+    """
+    a = Point((1, 0))
+    b = Point((1, 2))
+    c = Point((2, 2))
+    # y is just a construction point
+    y = Point((2, 1))
+    d = Point((3, 1))
+    e = Point((0, 1))
+    f = Point((4, 1))
+    nodes = GeoDataFrame(data={"geometry": [a, b, c, d, e, f]})
+    ad = LineString([a, b, c, y, d])
+    ef = LineString([e, f])
+    edges = GeoDataFrame(data={"geometry": [ad, ef]})
+    return snkit.Network(edges=edges, nodes=nodes)
+
+
+@fixture
+def split_heterogeneous_intersection():
+    """Crossing point and overlapping line, all edges split
+       b--c
+       |  |
+    e--x--y--d--f
+       |   --
+       a
+    """
+    a = Point((1, 0))
+    b = Point((1, 2))
+    c = Point((2, 2))
+    d = Point((3, 1))
+    e = Point((0, 1))
+    f = Point((4, 1))
+    x = Point((1, 1))
+    y = Point((2, 1))
+    # note: this is order sensitive although it shouldn't matter
+    nodes = GeoDataFrame(data={"geometry": [a, b, c, d, e, f, y, x]})
+    ax = LineString([a, x])
+    xb = LineString([x, b])
+    bc = LineString([b, c])
+    cy = LineString([c, y])
+    yd = LineString([y, d])
+    ex = LineString([e, x])
+    xy = LineString([x, y])
+    df = LineString([d, f])
+    # note that there are two edges 'yd'
+    edges = GeoDataFrame(data={"geometry": [ax, xb, bc, cy, yd, ex, xy, yd, df]})
+    return snkit.Network(edges=edges, nodes=nodes)
+
+
 @fixture
 def gap():
     """T-junction with nodes, edges not quite intersecting:
@@ -279,6 +436,55 @@ def test_split_at_intersections(unsplit_intersection, split_intersection):
     assert_frame_equal(split_intersection.nodes, actual.nodes)
 
 
+def test_split_at_intersection_already_split(split_intersection):
+    """Shouldn't do anything"""
+    actual = snkit.network.split_edges_at_intersections(split_intersection)
+    assert_frame_equal(split_intersection.edges, actual.edges)
+    assert_frame_equal(split_intersection.nodes, actual.nodes)
+
+
+def test_split_at_intersection_endnode(unsplit, split):
+    """Should split the edge at the endnode intersection
+
+    There shouldn't be any duplicate (no additional node).
+    """
+    actual = snkit.network.split_edges_at_intersections(unsplit)
+    assert_frame_equal(split.edges, actual.edges)
+    assert_frame_equal(split.nodes, actual.nodes)
+
+
+def test_split_at_intersection_multiple(
+    unsplit_multiple_intersections, split_multiple_intersections
+):
+    """Should split the edges at each intersection"""
+    actual = snkit.network.split_edges_at_intersections(unsplit_multiple_intersections)
+    assert_frame_equal(split_multiple_intersections.edges, actual.edges)
+    assert_frame_equal(split_multiple_intersections.nodes, actual.nodes)
+
+
+def test_split_intersection_overlapping_edges(
+    unsplit_overlapping_lines, split_overlapping_lines
+):
+    """Should split at the start and end of the intersecting sector
+
+    The intersecting sector should be duplicated.
+    """
+    actual = snkit.network.split_edges_at_intersections(unsplit_overlapping_lines)
+    assert_frame_equal(split_overlapping_lines.edges, actual.edges)
+    assert_frame_equal(split_overlapping_lines.nodes, actual.nodes)
+
+
+def test_split_intersection_heterogeneous(
+    unsplit_heterogeneous_intersection, split_heterogeneous_intersection
+):
+    """Should split at intersection points and sectors (endpoints)"""
+    actual = snkit.network.split_edges_at_intersections(
+        unsplit_heterogeneous_intersection
+    )
+    assert_frame_equal(split_heterogeneous_intersection.edges, actual.edges)
+    assert_frame_equal(split_heterogeneous_intersection.nodes, actual.nodes)
+
+
 def test_split_line():
     """Definitively split line at a point"""
     line = LineString(