# How to combine matrices with different size but preserve elements with same value?

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Steven Lai on 9 Jun 2021
Commented: Steven Lai on 9 Jun 2021
I have 4 columns of data which are FEM element number that share the same node (the elements are tetrahedron, hence 4 nodes) with one specific element, I want to merge them into one column so that when I select one element I can get all the elements that are connected with selected element.
for example
A= [1; 5; 8; 9], B=[1; 2; 4; 5; 7; 9]
and I want to get C=[1; 2; 4; 5; 7; 8; 9]
Is this possible?

Jan on 9 Jun 2021
Do you mean union?
A = [1; 5; 8; 9];
B = [1; 2; 4; 5; 7; 9];
C = union(A, B)
C = 7×1
1 2 4 5 7 8 9
Steven Lai on 9 Jun 2021
THANK YOU SO MUCH

Fangjun Jiang on 9 Jun 2021
unique([A;B])?

Steven Lord on 9 Jun 2021
None of A, B, or C have four columns like you stated you had.
You didn't indicate how you generated C from A and B, but one way to do so:
A= [1; 5; 8; 9];
B=[1; 2; 4; 5; 7; 9];
C = union(A, B)
C = 7×1
1 2 4 5 7 8 9
whos A B C % 1 column each
Name Size Bytes Class Attributes A 4x1 32 double B 6x1 48 double C 7x1 56 double
Steven Lai on 9 Jun 2021
A B and C are just example, I just want to make sure I can simplify my problem enough.
Union is perfect, even though I need to do it three times because it can't have more than 2 argument in it.
Thank you!