discrete conditional from vector of doubles

gtsam/discrete/DiscreteConditional.h

@@ -77,6 +77,18 @@ class GTSAM_EXPORT DiscreteConditional
                       const Signature::Table& table)
       : DiscreteConditional(Signature(key, parents, table)) {}
 
+  /**
+   * Construct from key, parents, and a vector<double> specifying the
+   * conditional probability table (CPT) in 00 01 10 11 order. For
+   * three-valued, it would be 00 01 02 10 11 12 20 21 22, etc....
+   *
+   * Example: DiscreteConditional P(D, {B,E}, table);
+   */
+  DiscreteConditional(const DiscreteKey& key, const DiscreteKeys& parents,
+                      const std::vector<double>& table)
+      : DiscreteConditional(1, DiscreteKeys{key} & parents,
+                            ADT(DiscreteKeys{key} & parents, table)) {}
+
   /**
    * Construct from key, parents, and a string specifying the conditional
    * probability table (CPT) in 00 01 10 11 order. For three-valued, it would

gtsam/discrete/DiscreteKey.h

@@ -74,6 +74,12 @@ namespace gtsam {
       return *this;
     }
 
+    /// Add multiple keys (non-const!)
+    DiscreteKeys& operator&(const DiscreteKeys& keys) {
+      this->insert(this->end(), keys.begin(), keys.end());
+      return *this;
+    }
+
     /// Print the keys and cardinalities.
     void print(const std::string& s = "",
                const KeyFormatter& keyFormatter = DefaultKeyFormatter) const;

gtsam/discrete/tests/testDiscreteConditional.cpp

@@ -46,6 +46,11 @@ TEST(DiscreteConditional, constructors) {
   DiscreteConditional actual2(1, f2);
   DecisionTreeFactor expected2 = f2 / *f2.sum(1);
   EXPECT(assert_equal(expected2, static_cast<DecisionTreeFactor>(actual2)));
+
+  std::vector<double> probs{0.2, 0.5, 0.3, 0.6, 0.4, 0.7, 0.25, 0.55, 0.35, 0.65, 0.45, 0.75};
+  DiscreteConditional actual3(X, {Y, Z}, probs);
+  DecisionTreeFactor expected3 = f2;
+  EXPECT(assert_equal(expected3, static_cast<DecisionTreeFactor>(actual3)));
 }
 
 /* ************************************************************************* */