How to determine the row in Matrix A based on the elements exist in another Matrix

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kiet tran 2019-11-18

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https://ww2.mathworks.cn/matlabcentral/answers/491726-how-to-determine-the-row-in-matrix-a-based-on-the-elements-exist-in-another-matrix

Hello Matlab community,

clear all; close all; clc
N = [1  1  5   1   1
   -10  1  5   5   0
     1 -4  1   8  -1]; % Node matrix
   
C_F = [1  2  3 
       4  3  2    ]; % Face matrix
   
   
n_F = size(C_F, 1); % Number of faces
C_E = []; % Creating empty matrix
for i = 1:n_F
    n1 = [C_F(i,1)]
        
    
    n2 = [C_F(i,2)]
    
    n3 = [C_F(i,3)]
    
    E = [n1 n2
         n2 n3
         n3 n1]
    %C_E = (C_E,E)
    C_E = vertcat(C_E,E);
    %C_E = unique(C_E,'rows');
    %C_E = sort(C_E,2);
    C_E = unique(sort(C_E,2),'rows');
   
end
       
figure() %  Creates Figure to plot C_F
for i = 1:n_F
    X = [ N(1, C_F(i,1));  N(1, C_F(i,2)); N(1, C_F(i,3))];
    Y = [ N(2, C_F(i,1));  N(2, C_F(i,2)); N(2, C_F(i,3))];
    Z = [ N(3, C_F(i,1));  N(3, C_F(i,2)); N(3, C_F(i,3))];
    C = [1];
    fill3(X,Y,Z,C)
    hold on % Keep adding things to the figure
end
axis equal % Plots axes with equal scale

The code that I have above determines C_F which is the matrix contains FACES, C_E which is the matrix that contains EDGES of each FACE in C_F, and a plotting figure for C_F. In the code above, C_F has 2 face. Face 1 is [1 2 3] that has edges [1 2, 2 3, 3 1] in C_E. Face 2 is [ 4 3 2] that has edges [4 3, 3 2, 2 4]. Respectively, C_E will have will have 5 rows because edge [2 3] and [3 2] are only one, no repeating edge in C_E.

Now, I have to determine matrix C_EF. Matrix C_EF will give me the surfaces that contains the edges in C_E. The number of rows of C_EF will be the number of edges in C_E. the number of columns will be the faces that contain the edge that the code is checking ( every face is triangle so each egde might be contained in a maximum of 2 possible faces)

For example: For edge [1 2] we have C_EF = [ 1 0 ] - first column in C_EF represent "face 1", and because no other faces so the other column is 0

For edge [2 3] we have C_EF =[ 1 2] - means face 1 and face 2 both contain edge [2 3]

My apologies if the question is kind of complicated. Because of it complex, I wasn't able to figure out the code for C_EF. Please help with this issue. Any suggestion is greatly appreciated. Thank you so much