MATLAB: Unique quad element list

Question

Dear all,

i am stuck with a small (easy) problem and need a hint.

Consider you have a non-unique element list t_quad with size(n_quad,4) and a corresponding non-unique point list p_quad with size(n_points,2).

Moreover, the point list also contains points which are never indexed by the element list.

I want to make both lists unique meaning i want to have a t_quad_unique list and a p_quad_unique list:

% Works!: This removes the non-unique elements and the corresponding points
[t_quad,~,~]=unique(t_quad,'rows');
[p_quad,~,b]=unique(p_quad,'rows');
t_quad(:)=b(t_quad(:));

Then after this i want to remove also the non-used points which are never used by the element list:

% Does not work!
[p_quad,~,b]=unique(p_quad(t_quad(:),:),'rows');
t_quad(:)=b(t_quad(:));

I lose some informations in this step. Where is the mistake?

Thanks for your help!

Edit:

Before:

After:

Answer 1

I answer my own question. This should work:

[t_quad,~,~]=unique(t_quad,'rows');
[p_quad,~,b]=unique(p_quad,'rows');
t_quad(:)=b(t_quad(:));
[p_unique,~,~]=unique(p_quad(t_quad(:),:),'rows');
[~,c]=ismember(p_quad,p_unique,'rows');
p_quad=p_unique;
t_quad(:)=c(t_quad(:));

Thanks anyway!