From dce8a6c341a2b0ecfb4f3a8e78e28c9604e52efb Mon Sep 17 00:00:00 2001
From: dellaert <dellaert@cc.gatech.edu>
Date: Tue, 4 Nov 2014 15:43:32 +0100
Subject: [PATCH] Improved error message

---
 gtsam/nonlinear/NonlinearFactor.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/gtsam/nonlinear/NonlinearFactor.cpp b/gtsam/nonlinear/NonlinearFactor.cpp
index 4824f3d0f..e9b97d644 100644
--- a/gtsam/nonlinear/NonlinearFactor.cpp
+++ b/gtsam/nonlinear/NonlinearFactor.cpp
@@ -18,6 +18,7 @@
 
 #include <gtsam/nonlinear/NonlinearFactor.h>
 #include <boost/make_shared.hpp>
+#include <boost/format.hpp>
 
 namespace gtsam {
 
@@ -79,7 +80,10 @@ bool NoiseModelFactor::equals(const NonlinearFactor& f, double tol) const {
 static void check(const SharedNoiseModel& noiseModel, size_t m) {
   if (noiseModel && m != noiseModel->dim())
     throw std::invalid_argument(
-        "NoiseModelFactor was created with a NoiseModel of incorrect dimension.");
+        boost::str(
+            boost::format(
+                "NoiseModelFactor: NoiseModel has dimension %1% instead of %2%.")
+                % noiseModel->dim() % m));
 }
 
 /* ************************************************************************* */