function svm = svm_node(n,x,y,elems,xc,yc,sig);
% function svm = svm_node(nodes,elems,sig);
% Interpolates element stresses to give stresses at a single node
%
%  n = node number
%  x,y = node location
%  elems = elem connection (3 or 4 cols for triangle, quad)
%  sig = stresses (3,:);
%
%  svm = von Mises stress at node
%
nargchk(6,6,nargin,'struct');
nelems = size(elems,1);
if size(sig,2) ~= nelems | size(sig,1) ~= 3
    error('Must provide three stresses per element');
end;
%
%  find elements that use each node and distance to centroid
%
[enum,jj] = ind2sub(size(elems),find(elems==n));
if isempty(enum)
    svm = [];
else
    dist = sqrt( (x-xc(enum)).^2 + (y-yc(enum)).^2 );
    wt = dist/sum(dist);
    nsig = sig(:,enum)*wt(:);
    sigx = nsig(1);
    sigy = nsig(2);
    tauxy = nsig(3);
    svm = (sigx-sigy)^2 + 6*tauxy^2;
    svm = sqrt(svm/2);
end;