single-value sample()

gtsam/discrete/DiscreteConditional.cpp

@@ -167,13 +167,13 @@ DecisionTreeFactor::shared_ptr DiscreteConditional::likelihood(
 
 /* ******************************************************************************** */
 DecisionTreeFactor::shared_ptr DiscreteConditional::likelihood(
-    size_t value) const {
+    size_t parent_value) const {
   if (nrFrontals() != 1)
     throw std::invalid_argument(
         "Single value likelihood can only be invoked on single-variable "
         "conditional");
   DiscreteValues values;
-  values.emplace(keys_[0], value);
+  values.emplace(keys_[0], parent_value);
   return likelihood(values);
 }
 
@@ -271,6 +271,17 @@ size_t DiscreteConditional::sample(const DiscreteValues& parentsValues) const {
   return distribution(rng);
 }
 
+/* ******************************************************************************** */
+size_t DiscreteConditional::sample(size_t parent_value) const {
+  if (nrParents() != 1)
+    throw std::invalid_argument(
+        "Single value sample() can only be invoked on single-parent "
+        "conditional");
+  DiscreteValues values;
+  values.emplace(keys_.back(), parent_value);
+  return sample(values);
+}
+
 /* ************************************************************************* */
 std::string DiscreteConditional::markdown(
     const KeyFormatter& keyFormatter) const {

gtsam/discrete/DiscreteConditional.h

@@ -145,7 +145,7 @@ public:
       const DiscreteValues& frontalValues) const;
 
   /** Single variable version of likelihood. */
-  DecisionTreeFactor::shared_ptr likelihood(size_t value) const;
+  DecisionTreeFactor::shared_ptr likelihood(size_t parent_value) const;
 
   /**
    * solve a conditional
@@ -161,6 +161,10 @@ public:
    */
   size_t sample(const DiscreteValues& parentsValues) const;
 
+
+  /// Single value version.
+  size_t sample(size_t parent_value) const;
+
   /// @}
   /// @name Advanced Interface
   /// @{

gtsam/discrete/discrete.i

@@ -81,6 +81,7 @@ virtual class DiscreteConditional : gtsam::DecisionTreeFactor {
   gtsam::DecisionTreeFactor* likelihood(size_t value) const;
   size_t solve(const gtsam::DiscreteValues& parentsValues) const;
   size_t sample(const gtsam::DiscreteValues& parentsValues) const;
+  size_t sample(size_t value) const;
   void solveInPlace(gtsam::DiscreteValues @parentsValues) const;
   void sampleInPlace(gtsam::DiscreteValues @parentsValues) const;
   string markdown(const gtsam::KeyFormatter& keyFormatter =

python/gtsam/tests/test_DiscreteConditional.py

@@ -20,7 +20,7 @@ from gtsam.utils.test_case import GtsamTestCase
 class TestDiscreteConditional(GtsamTestCase):
     """Tests for Discrete Conditionals."""
 
-    def test_likelihood(self):
+    def test_single_value_versions(self):
         X = (0, 2)
         Y = (1, 3)
         conditional = DiscreteConditional(X, [Y], "2/8 4/6 5/5")
@@ -33,6 +33,9 @@ class TestDiscreteConditional(GtsamTestCase):
         expected1 = DecisionTreeFactor(Y, "0.8 0.6 0.5")
         self.gtsamAssertEquals(actual1, expected1, 1e-9)
 
+        actual = conditional.sample(2)
+        self.assertIsInstance(actual, int)
+
     def test_markdown(self):
         """Test whether the _repr_markdown_ method."""