Pulling specific data from 2 different matrices, and starting a new matrix

I have a global matrix A of 4 column vectors and i've subsequently constructed 2 separate matrices X and Y from the 1st 2 columns of the global matrix. I want to construct a 3rd matrix using info from the 2 matrices X and Y. the statement will read value from X and Y then match these values in the global matrix A and read off the corresponding value from the 3rd column of A. Can someone advise on the best way to tackle this as my if else if statements are not working. Thats as far as ive got up to. Thanks Ernest

A = importdata(filename,delimiterIn,headerlinesIn);

%% Column vectors%%%%

x= A.data(:,1);

y= A.data(:,2)';

u =A.data(:,1:3);

v= A.data(:,4);

%% Matrices%%%%

n= length(A.data);

Mat_x= repmat(x,1,n); % 1 means the first element in the column is repeated in the row then the 2nd element repeated etc

Mat_y= repmat(y,n,1);

%% U population statement

u_rows= n;

u_col= n;

Mat_u= zeros(u_rows,u_col);

 for c= 1: u_col
     for r= 1:u_rows
         if 
             Mat_u(r,c)= u(r,c)

[Ernest Adisi]

for example

a= randi(10,10,4);

b= repmat(a(:,1),1,10);

c= repmat(a(:,2)',10,1);

for any element of c and any element of b i can go into a and read the corresponding value from the 3rd row of a