diff --git a/gtsam/discrete/DecisionTreeFactor.cpp b/gtsam/discrete/DecisionTreeFactor.cpp
index 0a453ad4a5..45574f6414 100644
--- a/gtsam/discrete/DecisionTreeFactor.cpp
+++ b/gtsam/discrete/DecisionTreeFactor.cpp
@@ -62,22 +62,6 @@ namespace gtsam {
     return error(values.discrete());
   }
 
-  /* ************************************************************************ */
-  AlgebraicDecisionTree<Key> DecisionTreeFactor::errorTree() const {
-    // Get all possible assignments
-    DiscreteKeys dkeys = discreteKeys();
-    // Reverse to make cartesian product output a more natural ordering.
-    DiscreteKeys rdkeys(dkeys.rbegin(), dkeys.rend());
-    const auto assignments = DiscreteValues::CartesianProduct(rdkeys);
-
-    // Construct vector with error values
-    std::vector<double> errors;
-    for (const auto& assignment : assignments) {
-      errors.push_back(error(assignment));
-    }
-    return AlgebraicDecisionTree<Key>(dkeys, errors);
-  }
-
   /* ************************************************************************ */
   double DecisionTreeFactor::safe_div(const double& a, const double& b) {
     // The use for safe_div is when we divide the product factor by the sum
diff --git a/gtsam/discrete/DecisionTreeFactor.h b/gtsam/discrete/DecisionTreeFactor.h
index 7ed1160166..7af729f3ef 100644
--- a/gtsam/discrete/DecisionTreeFactor.h
+++ b/gtsam/discrete/DecisionTreeFactor.h
@@ -141,7 +141,7 @@ namespace gtsam {
     }
 
     /// Calculate error for DiscreteValues `x`, is -log(probability).
-    double error(const DiscreteValues& values) const;
+    double error(const DiscreteValues& values) const override;
 
     /// multiply two factors
     DecisionTreeFactor operator*(const DecisionTreeFactor& f) const override {
@@ -292,9 +292,6 @@ namespace gtsam {
    */
   double error(const HybridValues& values) const override;
 
-  /// Compute error for each assignment and return as a tree
-  AlgebraicDecisionTree<Key> errorTree() const override;
-
   /// @}
 
    private:
diff --git a/gtsam/discrete/DiscreteFactor.cpp b/gtsam/discrete/DiscreteFactor.cpp
index b44d4fce2e..2b11046f44 100644
--- a/gtsam/discrete/DiscreteFactor.cpp
+++ b/gtsam/discrete/DiscreteFactor.cpp
@@ -50,6 +50,22 @@ double DiscreteFactor::error(const HybridValues& c) const {
   return this->error(c.discrete());
 }
 
+/* ************************************************************************ */
+AlgebraicDecisionTree<Key> DiscreteFactor::errorTree() const {
+  // Get all possible assignments
+  DiscreteKeys dkeys = discreteKeys();
+  // Reverse to make cartesian product output a more natural ordering.
+  DiscreteKeys rdkeys(dkeys.rbegin(), dkeys.rend());
+  const auto assignments = DiscreteValues::CartesianProduct(rdkeys);
+
+  // Construct vector with error values
+  std::vector<double> errors;
+  for (const auto& assignment : assignments) {
+    errors.push_back(error(assignment));
+  }
+  return AlgebraicDecisionTree<Key>(dkeys, errors);
+}
+
 /* ************************************************************************* */
 std::vector<double> expNormalize(const std::vector<double>& logProbs) {
   double maxLogProb = -std::numeric_limits<double>::infinity();
diff --git a/gtsam/discrete/DiscreteFactor.h b/gtsam/discrete/DiscreteFactor.h
index 771efbe5b4..19af5bd131 100644
--- a/gtsam/discrete/DiscreteFactor.h
+++ b/gtsam/discrete/DiscreteFactor.h
@@ -96,7 +96,7 @@ class GTSAM_EXPORT DiscreteFactor : public Factor {
   virtual double operator()(const DiscreteValues&) const = 0;
 
   /// Error is just -log(value)
-  double error(const DiscreteValues& values) const;
+  virtual double error(const DiscreteValues& values) const;
 
   /**
    * The Factor::error simply extracts the \class DiscreteValues from the
@@ -105,7 +105,7 @@ class GTSAM_EXPORT DiscreteFactor : public Factor {
   double error(const HybridValues& c) const override;
 
   /// Compute error for each assignment and return as a tree
-  virtual AlgebraicDecisionTree<Key> errorTree() const = 0;
+  virtual AlgebraicDecisionTree<Key> errorTree() const;
 
   /// Multiply in a DecisionTreeFactor and return the result as
   /// DecisionTreeFactor
@@ -158,8 +158,8 @@ class GTSAM_EXPORT DiscreteFactor : public Factor {
 // DiscreteFactor
 
 // traits
-template<> struct traits<DiscreteFactor> : public Testable<DiscreteFactor> {};
-
+template <>
+struct traits<DiscreteFactor> : public Testable<DiscreteFactor> {};
 
 /**
  * @brief Normalize a set of log probabilities.
@@ -177,7 +177,6 @@ template<> struct traits<DiscreteFactor> : public Testable<DiscreteFactor> {};
  * of the (unnormalized) log probabilities are either very large or very
  * small.
  */
-std::vector<double> expNormalize(const std::vector<double> &logProbs);
-
+std::vector<double> expNormalize(const std::vector<double>& logProbs);
 
 }  // namespace gtsam
diff --git a/gtsam/discrete/TableFactor.cpp b/gtsam/discrete/TableFactor.cpp
index b360617f56..f4e023a4da 100644
--- a/gtsam/discrete/TableFactor.cpp
+++ b/gtsam/discrete/TableFactor.cpp
@@ -168,11 +168,6 @@ double TableFactor::error(const HybridValues& values) const {
   return error(values.discrete());
 }
 
-/* ************************************************************************ */
-AlgebraicDecisionTree<Key> TableFactor::errorTree() const {
-  return toDecisionTreeFactor().errorTree();
-}
-
 /* ************************************************************************ */
 DecisionTreeFactor TableFactor::operator*(const DecisionTreeFactor& f) const {
   return toDecisionTreeFactor() * f;
diff --git a/gtsam/discrete/TableFactor.h b/gtsam/discrete/TableFactor.h
index 228b363376..f0ecd66a3f 100644
--- a/gtsam/discrete/TableFactor.h
+++ b/gtsam/discrete/TableFactor.h
@@ -179,7 +179,7 @@ class GTSAM_EXPORT TableFactor : public DiscreteFactor {
   double operator()(const DiscreteValues& values) const override;
 
   /// Calculate error for DiscreteValues `x`, is -log(probability).
-  double error(const DiscreteValues& values) const;
+  double error(const DiscreteValues& values) const override;
 
   /// multiply two TableFactors
   TableFactor operator*(const TableFactor& f) const {
@@ -358,9 +358,6 @@ class GTSAM_EXPORT TableFactor : public DiscreteFactor {
    */
   double error(const HybridValues& values) const override;
 
-  /// Compute error for each assignment and return as a tree
-  AlgebraicDecisionTree<Key> errorTree() const override;
-
   /// @}
 };
 
diff --git a/gtsam/hybrid/tests/Switching.h b/gtsam/hybrid/tests/Switching.h
index 1b176ad654..64025397ff 100644
--- a/gtsam/hybrid/tests/Switching.h
+++ b/gtsam/hybrid/tests/Switching.h
@@ -158,7 +158,7 @@ struct Switching {
     nonlinearFactorGraph.emplace_shared<PriorFactor<double>>(
         X(0), measurements.at(0), Isotropic::Sigma(1, prior_sigma));
 
-    // Add "motion models" ϕ(X(k),X(k+1)).
+    // Add "motion models" ϕ(X(k),X(k+1),M(k)).
     for (size_t k = 0; k < K - 1; k++) {
       auto motion_models = motionModels(k, between_sigma);
       nonlinearFactorGraph.emplace_shared<HybridNonlinearFactor>(modes[k],