function  [MUA,k,l]=DeactivateMUAelements(CtrlVar,MUA,ElementsToBeDeactivated,kIn,lIn)

Deactivates elements in the list

ElementsToBeDeactivated

The variable ElementsToBeDeactivated can be either a logical or an index array.

kIn and lIn are optional inputs.

Nodes that are no longer part of the FE mesh are deleted and the connectivity updated accordingly

If CtrlVar.sweep is true, elements and nodes are then renumbered.

k gives me the mapping between new and old node numbers, that is:

     j=k(i)

gives the old node number j for the new node number i

If needed, one can transfer/map the old nodal values, fOld, onto the new subset of nodes using:

   fNew=fOld(k) ;

and

fNew(i)=fOld(k(i)) ;

where fNew are the nodal values over the new mesh MUA (ie MUA returned).

l gives the mapping between old and new nodes numbers, that is:

      i=l(j)

gives the new node number i for the old node number j.

l(j)=nan

if no node in the new mesh corresponds to the old node j, ie for all deleted nodes.

To get a list of deleted old node numbers use:

find(isnan(l))

And to get a logical list of the nodes on the old mesh that were kept in the new:

~isnan(l)             ;   % logical list of nodes in the old mesh used/kept in the new mesh.

If elements are deactivated repeatedly and one needs to know the mapping between the original and the final mesh do:

k=k1(k2(k3))     % where k1 results from the first, k2 from the second, etc, deactivations

and then:

   l=1:nNodesIn ; l=l(:)+nan;
   l(k(1:numel(k)))=1:numel(k);

where nNodesIn is the number of nodes in the initial mesh, i.e. before the first round of deactivations. Alternativily, provide k and l from the previous deactivation as an input. These are the optional input variables kIn and lIn. The k and l will then be updated as k=kIn(k), providing the mapping with respect to the original mesh.

narginchk(3,5)


% This works equally for both logical and index arrays.
if ~any(ElementsToBeDeactivated)
    k=1:MUA.Nnodes;
    l=1:MUA.Nnodes;
    return
end

nNodesIn=MUA.Nnodes;




MUA.connectivity(ElementsToBeDeactivated,:)=[];

% eliminate MUA.coordinates that are no longer part of mesh, and update MUA.connectivity accordingly
[k,~,ic]=unique(MUA.connectivity(:));
MUA.connectivity=reshape(ic,size(MUA.connectivity));
MUA.coordinates=MUA.coordinates(k,:);


% K is the subset of nodes that I keep.
%
% Assuming there are no further changes to the nodal numbering, if I wanted to interpolate, I could do xNew=xOld(k) ;

% renumber nodes and elements
if CtrlVar.sweep
    [MUA.coordinates,MUA.connectivity,p] = NodalSweep(MUA.coordinates,MUA.connectivity,CtrlVar.SweepAngle);
    [MUA.coordinates,MUA.connectivity] = ElementSweep(MUA.coordinates,MUA.connectivity,CtrlVar.SweepAngle);
    k=k(p) ;   % keep track of how k changes
end

if CtrlVar.UpdateMUAafterDeactivating
    MUA=UpdateMUA(CtrlVar,MUA);
else
    MUA.M=[];
    MUA.Deriv=[];
    MUA.DetJ=[];
    MUA.TR=[];
    MUA.Boundary=[];
    MUA.dM=[];
    MUA.xEle=[];
    MUA.yEla=[];
    MUA.Nnodes=size(MUA.coordinates,1);
    MUA.Nele=size(MUA.connectivity,1);
    MUA.EleAreas=TriAreaFE(MUA.coordinates,MUA.connectivity); % areas for each element
    MUA.Area=sum(MUA.EleAreas);

end

if nargin>4  && ~isempty(kIn)
    k=kIn(k);
end



if nargout==3   % create a mapping from old to new node numbers
    if nargin==5  && ~isempty(lIn)
        l=lIn+nan;
    else
        %l=1:nNodesIn ; l=l(:)+nan;
        l=nan(nNodesIn,1) ;
    end
    l(k(1:numel(k)))=1:numel(k);
end


% MUA.RefineMesh=[] ; %  As I now have a new mesh I need to reset the newest vertex bisection data structure.
%                    %  Therefore no further unrefinement over the previous mesh can be done.

end

Published with MATLAB® R2023b