New function MeanClusteringCoefficient

Author: axkr

symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/reflection/system/MeanClusteringCoefficient.java

@@ -0,0 +1,59 @@
+package org.matheclipse.core.reflection.system;
+
+import org.jgrapht.Graph;
+import org.matheclipse.core.builtin.GraphFunctions;
+import org.matheclipse.core.eval.EvalEngine;
+import org.matheclipse.core.eval.interfaces.AbstractFunctionEvaluator;
+import org.matheclipse.core.expression.F;
+import org.matheclipse.core.expression.ImplementationStatus;
+import org.matheclipse.core.expression.data.GraphExpr;
+import org.matheclipse.core.interfaces.IAST;
+import org.matheclipse.core.interfaces.IASTAppendable;
+import org.matheclipse.core.interfaces.IExpr;
+
+/**
+ * Returns the mean clustering coefficient for a graph. This is computed as the arithmetic mean of
+ * the local clustering coefficients of all the vertices in the graph.
+ */
+public class MeanClusteringCoefficient extends AbstractFunctionEvaluator {
+
+  @Override
+  public IExpr evaluate(final IAST ast, EvalEngine engine) {
+    if (ast.argSize() == 1) {
+      GraphExpr<?> gex = GraphFunctions.getGraphExpr(ast.arg1());
+      if (gex == null) {
+        return F.NIL;
+      }
+
+      @SuppressWarnings("unchecked")
+      Graph<IExpr, ?> g = gex.toData();
+      boolean isDirected = g.getType().isDirected();
+
+      IAST vertices = GraphExpr.vertexToIExpr(g);
+      int n = vertices.argSize();
+      if (n == 0) {
+        return F.C0;
+      }
+
+      // Sum the individual local clustering coefficients
+      IASTAppendable sumPlus = F.PlusAlloc(n);
+      for (int i = 1; i <= n; i++) {
+        sumPlus.append(LocalClusteringCoefficient.getLocalCC(g, vertices.get(i), isDirected));
+      }
+
+      // Automatically evaluate and simplify the fraction: (Sum / N)
+      return engine.evaluate(F.Divide(sumPlus, F.ZZ(n)));
+    }
+    return F.NIL;
+  }
+
+  @Override
+  public int[] expectedArgSize(IAST ast) {
+    return ARGS_1_1;
+  }
+
+  @Override
+  public int status() {
+    return ImplementationStatus.PARTIAL_SUPPORT;
+  }
+}