how to find out node coordinates for a simple quad element?

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S Priya on 16 Aug 2021
Commented: S Priya on 17 Aug 2021
I want to know how to find out the node co-ordinates for a simple shell element?

Wan Ji on 16 Aug 2021
Edited: Wan Ji on 16 Aug 2021
Hi, friend! It seems you are studying the finite element method.
For fem analysis, two important things for preprocessing are nodes and elements.
Usually nodes are stored in a n-by-d matrix (n is the number of nodes, d is the dimension), for example
nodes = [0,0,0; 1,0,0; 1,1,0; 0,1,0; 0,2,1; 1,2,1];
elements are stored in a m-by-s matrix, in a quad element with 4 nodes, s=4, and m is the number of elements. Elements record the node identity and their arrangement in an element. Here two elements are
elements = [1,2,3,4; 3,4,5,6];
IF YOU want show the two shell elements, then use patch function
patch('vertices', nodes, 'faces', elements, 'facevertexcdata', nodes(:,3),'facecolor','interp')
colormap(jet)
IF you want get the nodes of the second elements, just do
ecoor = nodes(element(2,:),:)
ecoor =
1 1 0
0 1 0
0 2 1
1 2 1
Here 2 represents the second element.

Fabio Freschi on 16 Aug 2021
It depends on your data structure: now your qeustion is rather vague.
Assuming that you have the node coordinates in the Nx3 array P and the connectivity matrix in the the Mx4 array T and you want to know the node coordinates of the element idx, you may write
Pelem = P(T(idx,:),:);
S Priya on 17 Aug 2021
I have only the relations between the x, y and z coordinates for the shell facet (quad) element. what would be the further steps for carrying the fem analysis?