diff --git a/gtsam.h b/gtsam.h
index 2ab182b24..6ad907cd0 100644
--- a/gtsam.h
+++ b/gtsam.h
@@ -829,6 +829,7 @@ class SymbolicFactorGraph {
   void print(string s) const;
   bool equals(const gtsam::SymbolicFactorGraph& rhs, double tol) const;
   size_t size() const;
+  bool exists(size_t idx) const;
 
   // Standard interface
   gtsam::KeySet keys() const;
@@ -1246,6 +1247,7 @@ class GaussianFactorGraph {
   size_t size() const;
   gtsam::GaussianFactor* at(size_t idx) const;
   gtsam::KeySet keys() const;
+  bool exists(size_t idx) const;
 
   // Building the graph
   void push_back(gtsam::GaussianFactor* factor);
@@ -1520,6 +1522,7 @@ class NonlinearFactorGraph {
   gtsam::NonlinearFactor* at(size_t idx) const;
   void push_back(const gtsam::NonlinearFactorGraph& factors);
   void push_back(gtsam::NonlinearFactor* factor);
+  bool exists(size_t idx) const;
 
   // NonlinearFactorGraph
   double error(const gtsam::Values& values) const;
diff --git a/gtsam/inference/FactorGraph.h b/gtsam/inference/FactorGraph.h
index e8c10d532..9928c9c81 100644
--- a/gtsam/inference/FactorGraph.h
+++ b/gtsam/inference/FactorGraph.h
@@ -352,6 +352,9 @@ namespace gtsam {
     /** Potentially very slow function to return all keys involved */
     FastSet<Key> keys() const;
 
+    /** MATLAB interface utility: Checks whether a factor index idx exists in the graph and is a live pointer */
+    inline bool exists(size_t idx) const { return idx < size() && at(idx); }
+
   private:
 
     /** Serialization function */