ldg_local_mass_matrix.m

function M = ldg_local_mass_matrix(qdeg,df_info)
%function M = ldg_local_mass_matrix(qdeg,df_info)
%
% function computing the local mass matrix of a scalar ldg basis by
% numerical integration of degree qdeg. 
%
% Result is a numlocal_base_function x num_local_base_functions
% matrix with entries
%``\int_{\mbox{ref}_{\mbox{tria}}} \hat \phi_i \hat \phi_j.``
%
% The matrix should be unity due to orthonormalization of the
% basis, but due to numerical errors, this can be slightly different.

% Bernard Haasdonk 31.8.2009

f = @(lcoord) gram_matrix(ldg_evaluate_basis(lcoord,df_info)');
M = triaquadrature(qdeg,f);
%| \docupdate