index_ext.m

function einds_ext = index_ext(grid, einds, neigh_steps)
%function einds_ext = index_ext(grid, einds, neigh_steps)
%
% function computing the sorted list of element indicés, which are
% given by the neigh_steps number of neighbours of the elements with
% indices einds in grid.
% e.g. for neigh_steps = 0: einds_ext = einds 
% e.g. for neigh_steps = 1: einds_ext = einds plus all edge-neighbours
%      of elements 
% e.g. for neigh_steps = 2: einds_ext = einds plus all edge-neighbours
%      of elements plus all edge neighbours of these.

% Bernard Haasdonk 18.6.2010

mask = zeros(1,grid.nelements);
mask(einds) = 1;
einds_ext = einds;
for n = 1:neigh_steps
  nbi  = grid.NBI(einds_ext,:);
  i    = find(nbi>0);
  mask(nbi(i)) = n+1;
  einds_ext = find(mask>0);
end;