use matrixbase for inputs

Former-commit-id: f8a4dc9b0496392441774f03af2a50540789c730

include/igl/matlab_format.cpp

@@ -11,7 +11,7 @@
 
 template <typename DerivedM>
 IGL_INLINE const Eigen::WithFormat< DerivedM > igl::matlab_format(
-  const Eigen::PlainObjectBase<DerivedM> & M,
+  const Eigen::MatrixBase<DerivedM> & M,
   const std::string name)
 {
   using namespace std;

include/igl/matlab_format.h

@@ -42,7 +42,7 @@ namespace igl
   // // ];
   template <typename DerivedM>
   IGL_INLINE const Eigen::WithFormat< DerivedM > matlab_format(
-    const Eigen::PlainObjectBase<DerivedM> & M,
+    const Eigen::MatrixBase<DerivedM> & M,
     const std::string name = "");
   // Same but for sparse matrices. Print IJV format into an auxillary variable
   // and then print a call to sparse which will construct the sparse matrix