Same Community function

algo/src/main/java/org/neo4j/graphalgo/linkprediction/LinkPrediction.java

@@ -119,6 +119,17 @@ public double totalNeighbors(@Name("node1") Node node1, @Name("node2") Node node
         return neighborsFinder.findNeighbors(node1, node2, relationshipType, direction).size();
     }
 
+    @UserFunction("algo.linkprediction.sameCommunity")
+    @Description("algo.linkprediction.sameCommunity(node1:Node, node2:Node, communityProperty: String) " +
+            "given two nodes, indicates if they have the same community")
+    public double sameCommunity(@Name("node1") Node node1, @Name("node2") Node node2,
+                                 @Name(value = "communityProperty", defaultValue = "community") String communityProperty) {
+        if(!node1.hasProperty(communityProperty) || !node2.hasProperty(communityProperty)) {
+            return 0.0;        }
+
+        return node1.getProperty(communityProperty).equals(node2.getProperty(communityProperty)) ? 1.0 : 0.0;
+    }
+
     private int degree(Node node, RelationshipType relationshipType, Direction direction) {
         return relationshipType == null ? node.getDegree(direction) : node.getDegree(relationshipType, direction);
     }

tests/src/test/java/org/neo4j/graphalgo/algo/linkprediction/SameCommunityProcIntegrationTest.java

@@ -0,0 +1,130 @@
+/**
+ * Copyright (c) 2017 "Neo4j, Inc." <http://neo4j.com>
+ *
+ * This file is part of Neo4j Graph Algorithms <http://github.com/neo4j-contrib/neo4j-graph-algorithms>.
+ *
+ * Neo4j Graph Algorithms is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.neo4j.graphalgo.algo.linkprediction;
+
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.neo4j.graphalgo.linkprediction.LinkPrediction;
+import org.neo4j.graphdb.GraphDatabaseService;
+import org.neo4j.graphdb.Result;
+import org.neo4j.graphdb.Transaction;
+import org.neo4j.graphdb.factory.GraphDatabaseSettings;
+import org.neo4j.kernel.impl.proc.Procedures;
+import org.neo4j.kernel.internal.GraphDatabaseAPI;
+import org.neo4j.test.TestGraphDatabaseFactory;
+
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+
+public class SameCommunityProcIntegrationTest {
+    private static final String SETUP =
+            "CREATE (mark:Person {name: 'Mark'})\n" +
+            "SET mark.community=1, mark.partition = 4\n" +
+            "CREATE (michael:Person {name: 'Michael'})\n" +
+            "SET michael.community=2, michael.partition=4\n" +
+            "CREATE (praveena:Person {name: 'Praveena'})\n" +
+            "SET praveena.community=1\n" +
+            "CREATE (jennifer:Person {name: 'Jennifer'})\n";
+
+    private static GraphDatabaseService db;
+
+    @BeforeClass
+    public static void setUp() throws Exception {
+        db = new TestGraphDatabaseFactory()
+                .newImpermanentDatabaseBuilder()
+                .setConfig(GraphDatabaseSettings.procedure_unrestricted,"algo.*")
+                .newGraphDatabase();
+
+        ((GraphDatabaseAPI) db).getDependencyResolver()
+                .resolveDependency(Procedures.class)
+                .registerFunction(LinkPrediction.class);
+
+        db.execute(SETUP).close();
+    }
+
+    @AfterClass
+    public static void tearDown() {
+        db.shutdown();
+    }
+
+    @Test
+    public void missingProperty() throws Exception {
+        String controlQuery =
+                "MATCH (p1:Person {name: 'Jennifer'})\n" +
+                        "MATCH (p2:Person {name: 'Mark'})\n" +
+                        "RETURN algo.linkprediction.sameCommunity(p1, p2) AS score, " +
+                        "       0.0 AS cypherScore";
+
+        try (Transaction tx = db.beginTx()) {
+            Result result = db.execute(controlQuery);
+            Map<String, Object> node = result.next();
+            assertEquals((Double) node.get("cypherScore"), (double) node.get("score"), 0.01);
+        }
+    }
+
+    @Test
+    public void sameCommunity() throws Exception {
+        String controlQuery =
+                "MATCH (p1:Person {name: 'Praveena'})\n" +
+                        "MATCH (p2:Person {name: 'Mark'})\n" +
+                        "RETURN algo.linkprediction.sameCommunity(p1, p2) AS score, " +
+                        "       1.0 AS cypherScore";
+
+        try (Transaction tx = db.beginTx()) {
+            Result result = db.execute(controlQuery);
+            Map<String, Object> node = result.next();
+            assertEquals((Double) node.get("cypherScore"), (double) node.get("score"), 0.01);
+        }
+    }
+
+    @Test
+    public void differentCommunity() throws Exception {
+        String controlQuery =
+                "MATCH (p1:Person {name: 'Michael'})\n" +
+                        "MATCH (p2:Person {name: 'Mark'})\n" +
+                        "RETURN algo.linkprediction.sameCommunity(p1, p2) AS score, " +
+                        "       0.0 AS cypherScore";
+
+        try (Transaction tx = db.beginTx()) {
+            Result result = db.execute(controlQuery);
+            Map<String, Object> node = result.next();
+            assertEquals((Double) node.get("cypherScore"), (double) node.get("score"), 0.01);
+        }
+    }
+
+    @Test
+    public void specifyProperty() throws Exception {
+        String controlQuery =
+                "MATCH (p1:Person {name: 'Michael'})\n" +
+                        "MATCH (p2:Person {name: 'Mark'})\n" +
+                        "RETURN algo.linkprediction.sameCommunity(p1, p2, 'partition') AS score, " +
+                        "       1.0 AS cypherScore";
+
+        try (Transaction tx = db.beginTx()) {
+            Result result = db.execute(controlQuery);
+            Map<String, Object> node = result.next();
+            assertEquals((Double) node.get("cypherScore"), (double) node.get("score"), 0.01);
+        }
+    }
+
+
+
+}