feat: Graph.Nearest_Neighbor_Graph() #851
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Pull Request Overview
This PR introduces a new graph generator function Graph.Nearest_Neighbor_Graph() to python-igraph, which creates k-nearest neighbor graphs from spatial point data. The implementation serves as an example for exposing additional graph generators, specifically to guide the future implementation of a Delaunay generator.
Key changes:
- Adds C implementation of the nearest neighbor graph generator with support for different metrics (euclidean, manhattan) and configurable parameters
- Includes Python binding and method registration for the new graph generator
- Adds basic test coverage for the new functionality
Reviewed Changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| src/_igraph/graphobject.c | Implements the C function and registers the Python method for nearest neighbor graph generation |
| src/_igraph/convert.h | Declares the metric conversion function for parameter parsing |
| src/_igraph/convert.c | Implements conversion from Python objects to igraph metric types |
| tests/test_generators.py | Adds basic test case for the new graph generator |
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szhorvat
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| * Spatial graphs * | ||
| **********************************************************************/ | ||
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| PyObject *igraphmodule_Graph_Nearest_Neighbor_Graph(PyTypeObject *type, |
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| PyObject *igraphmodule_Graph_Nearest_Neighbor_Graph(PyTypeObject *type, | |
| PyObject *igraphmodule_Graph_Nearest_Neighbor(PyTypeObject *type, |
| def testNearestNeighborGraph(self): | ||
| points = [[0,0], [1,2], [-3, -3]] | ||
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| g = Graph.Nearest_Neighbor_Graph(points) |
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| g = Graph.Nearest_Neighbor_Graph(points) | |
| g = Graph.Nearest_Neighbor(points) |
| self.assertEqual(g.vcount(), 3) | ||
| self.assertEqual(g.ecount(), 2) | ||
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| g = Graph.Nearest_Neighbor_Graph(points, directed=True) |
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| g = Graph.Nearest_Neighbor_Graph(points, directed=True) | |
| g = Graph.Nearest_Neighbor(points, directed=True) |
| self.assertEqual(g.ecount(), 3) | ||
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| # expecting a complete graph | ||
| g = Graph.Nearest_Neighbor_Graph(points, k=2) |
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| g = Graph.Nearest_Neighbor_Graph(points, k=2) | |
| g = Graph.Nearest_Neighbor(points, k=2) |
@Zepeacedust, this is an example of exposing a new graph generator in python-igraph, that you can later use as a model to expose the Delaunay generator.
This is not my comfort zone so let's wait for comments from @ntamas.
@ntamas, do you prefer
Nearest_Neighbor_GraphorNearest_Neighborhere? Since this term is used in other contexts as well, I vote for keeping the Graph suffix.