minor fixes

lib/TabFunction.cpp

@@ -68,7 +68,10 @@ double TabFunction::operator()(const double *arg) const
     
     if ((x < value_.begin()->first)||(x >= value_.rbegin()->first))
     {
-        LATAN_ERROR(Range, "tabulated function variable out of range");
+        LATAN_ERROR(Range, "tabulated function variable out of range (x= "
+                    + strFrom(x) + " not in ["
+                    + strFrom(value_.begin()->first) + ", "
+                    + strFrom(value_.rbegin()->first) + "])");
     }
     
     auto i    = value_.equal_range(x);

lib/XYSampleData.hpp

@@ -53,7 +53,7 @@ public:
                                           const Index j = 0) const;
 private:
     DSample                           chi2_;
-    Index                             nDof_{0};
+    double                            nDof_{0.};
     std::vector<DoubleFunctionSample> model_;
 };