onedgrid_gridpart_old.m

function gpart = onedgrid_gridpart(grid,eind);
%function gpart = onedgrid_gridpart(grid,eind);
%
% function extracting a subgrid of grid with given indices and
% correct neighbour information.
if (sort(eind)~=eind)
  error('eind not sorted!');
end;
gpart.nelements = length(eind);
gpart.eind = eind;
% initally mark all neighbours to non-existing
gpart.NBI = -10 * ones(length(eind),2); 
% set existing right neighbours
ndiff = [eind(2:end),0] - eind; % ndiff==1 if left neighbour in eind
i = find(ndiff==1);
gpart.NBI(i,1) = i+1;    
% set existing left neighbours
ndiff = eind - [1e10, eind(1:end-1)]; % ndiff==1 if left neighbour in eind
i = find(ndiff==1);
gpart.NBI(i,2) = i-1;    
% set existing dirichlet-boundary
if eind(1) == 1
  gpart.NBI(1,2)= grid.NBI(1,2);
end;
if eind(end) == grid.nelements
  gpart.NBI(end,1)= grid.NBI(end,1);
end;