From: Brent Kraczek <bkraczek@ic...>  20090116 21:07:12

Dear all, I am trying to use functions from the MeshFunction class in a test file I have adapted from example 3. In particular, I would like to calculate the gradient at a given point. I'm having trouble figuring out what variables are needed for the constructor: So here are the constructor declarations from mesh_function.h: /** * Constructor for mesh based functions with vectors * as return value. Optionally takes a master function. * If the MeshFunction is to be evaluated outside of the * local partition of the mesh, then both the mesh in * \p eqn_systems and the coefficient vector \p vec * should be serialized. */ MeshFunction (const EquationSystems& eqn_systems, const NumericVector<Number>& vec, const DofMap& dof_map, const std::vector<unsigned int>& vars, const FunctionBase* master=NULL); /** * Constructor for mesh based functions with a number * as return value. Optionally takes a master function. * If the MeshFunction is to be evaluated outside of the * local partition of the mesh, then both the mesh in * \p eqn_systems and the coefficient vector \p vec * should be serialized. */ MeshFunction (const EquationSystems& eqn_systems, const NumericVector<Number>& vec, const DofMap& dof_map, const unsigned int var, const FunctionBase* master=NULL); eqn_systems and dof_map are clear. It says that vec (internally, _vector) holds the data to be interpolated. I thought this was part of eqn_system . I appears to me that var/vars is supposed to be the number of the attached variables (in this case, just "u"). Since I have only one field, should this be '0'? Finally, I'm not completely sure what FunctionBase does (am I okay leaving it blank). Sorry for all my n00b questions, and thanks for your help. Brent 