neighborelem.m

function [conn,connnum,count]=neighborelem(elem,nn);
%
% [conn,connnum,count]=neighborelem(elem,nn)
%
% create node neighbor list from a mesh
%
% author: Qianqian Fang, <q.fang at neu.edu>
% date: 2007/11/21
%
% input:
%    elem:  element table of a mesh
%    nn  :  total node number of the mesh
%
% output:
%    conn:  output, a cell structure of length nn, conn{n}
%           contains a list of all neighboring elem ID for node n
%    connnum: vector of length nn, denotes the neighbor number of each node
%    count: total neighbor numbers
%
% -- this function is part of iso2mesh toolbox (http://iso2mesh.sf.net)
%

conn=cell(nn,1);
dim=size(elem);
for i=1:dim(1)
  for j=1:dim(2)
    conn{elem(i,j)}=[conn{elem(i,j)},i];
  end
end
count=0;
connnum=zeros(1,nn);
for i=1:nn
    conn{i}=sort(conn{i});
    connnum(i)=length(conn{i});
    count=count+connnum(i);
end