minor typo fixes

gtsam/hybrid/tests/Switching.h

@@ -147,7 +147,7 @@ struct Switching {
     }
 
     // Create hybrid factor graph.
-    // Add a prior on X(1).
+    // Add a prior on X(0).
     auto prior = boost::make_shared<PriorFactor<double>>(
         X(0), measurements.at(0), noiseModel::Isotropic::Sigma(1, prior_sigma));
     nonlinearFactorGraph.push_nonlinear(prior);

gtsam/hybrid/tests/testHybridBayesTree.cpp

@@ -105,7 +105,7 @@ TEST(HybridBayesTree, Optimize) {
     graph1.push_back(s.linearizedFactorGraph.at(i));
   }
 
-  // Add the Gaussian factors, 1 prior on X(1),
+  // Add the Gaussian factors, 1 prior on X(0),
   // 3 measurements on X(2), X(3), X(4)
   graph1.push_back(s.linearizedFactorGraph.at(0));
   for (size_t i = 4; i <= 6; i++) {