function int=grinprodgausnode(g,I);%grinprodgausnode Computes the gradient part of the system matrix %in the linear basis case. The conductivity  is also in the linear basis. % Function int=grinprodgausnode(g,I);% computes the gradient part of the system matrix % in the linear basis case. The conductivity  is also in the linear basis. %% INPUT%% g = nodes of the element% I = index of  the chosen node (optional)%% OUTPUT%% int = three dimensional array or 3x3 matrix of the values of integral% P. Ronkanen and M. Vauhkonen 10.5. 1996. Modified by M. Vauhkonen for EIDORS% 11.5.2000.% University of Kuopio, Department of Applied Physics, PO Box 1627,% FIN-70211 Kuopio, Finland, email: Marko.Vauhkonen@uku.fiw=[1/6*ones(3,1)];ip=[1/2 0;1/2 1/2;0 1/2];L=[-1 1 0;-1 0 1];Jt=L*g;iJt=inv(Jt);dJt=abs(det(Jt));G=iJt*L;GdJt=G'*G*dJt;msg=max(size(g));if nargin > 1 S=[[1-ip(1,1)-ip(1,2);ip(1,1);ip(1,2)],[1-ip(2,1)-ip(2,2);ip(2,1);ip(2,2)],[1-ip(3,1)-ip(3,2);ip(3,1);ip(3,2)]]*w; int=S(I)*GdJt;else  int=zeros(msg,msg,3);  S=[[1-ip(1,1)-ip(1,2);ip(1,1);ip(1,2)],[1-ip(2,1)-ip(2,2);ip(2,1);ip(2,2)],[1-ip(3,1)-ip(3,2);ip(3,1);ip(3,2)]]*w; for jj=1:3  int(:,:,jj)=S(jj)*GdJt; endend