I use FreeFem++ to get the matrices of a given problem and then solve the system in Matlab for some reason. I build the matrices with P2 elements. However I need to export the label (for boundary elements) of each node of the fespace P2. So far I succeeded to have the region(s) of each nodes, but still have issues to get the label of “boundary nodes”.
Does someone know how to do it?

Thank you for your answer. I agree that It wasn’t clear.

Given a boundary label, (label = 1 for instance). Is it possible to export the nodes whose label=1 when dealing with P2 elements. By exporting the node I mean to export the number of the node nb_node such that x[][nb_node] should be its x coordinate.