expose fmatrixs

booster/xgboost_data.h

@@ -378,7 +378,7 @@ namespace xgboost{
                     utils::Assert(fi.Read(&data[0], data.size() * sizeof(REntry)), "Load FMatrixS");
                 }
             }
-        protected:
+        public:
             /*! \brief row pointer of CSR sparse storage */
             std::vector<size_t>  row_ptr_;
             /*! \brief data in the row */