base/ElemMassWMat2DP1.m

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function AElem=ElemMassWMat2DP1(area,w)
% function AElem=ElemMassWMat2DP1(area,w)
%   Computation of the element weighted mass matrix for
%  `P_1`-Lagrange finite elements
%   
% Parameters:
%  area: triangle area
%  w: values of the weight function at the triangle vertices,
%  `3\times 1` array
%  
% Return values:
%  AElem: Element weighted mass matrix, `3\times 3` matrix
%
% Example:
%  @verbatim 
%    area=1/2.;
%    w=ones(3,1);
%    AElem=ElemMassWMat2DP1(area);
%  @endverbatim
% Copyright:
%   See \ref license
  AElem=(area/30)*[ 3*w(1)+w(2)+w(3), w(1)+w(2)+w(3)/2, w(1)+w(2)/2+w(3); ...
                    w(1)+w(2)+w(3)/2, w(1)+3*w(2)+w(3), w(1)/2+w(2)+w(3); ...
                    w(1)+w(2)/2+w(3), w(1)/2+w(2)+w(3), w(1)+w(2)+3*w(3)];