sorting and selecting data within a matrix to match two columns.

I have two matrices in which there are tow columns with unique identifiers. The 1st matrix is much bigger (207000*4) dimensions. The second is (14680*5). Column 1 from 1st matrix has values that appear more than once, and are identical to the values from column 1, matrix. I would like to attach the the two matrices by column one. So for example, if Column1, Matrix 1 value is 1650, then pick the row from Matrix 2 with same unique ID (1650) and add it to Matrix1 or into a new output matrix. Please see example excel table picture attached.

Answer 1

[KSSV]

 clc; clear all ;
 % Generate matrix1
 pos1 = randsample(1:100,30)' ;          % First column of matrix1 / id's
 matrix1 = [pos1 rand(length(pos1),3)] ; % Data of matrix1
 % Generate matrix2
 pos2 = randsample(1:100,20)' ;          % First column of matrix2 / id's
 matrix2 = [pos2 rand(length(pos2),3)] ; % Data of matrix2
 % Make new matrix from first columns of matrix1 and matrix2 
 newmatrix = [] ;
 myidx = [] ;
 % Loop for comparing id's
 for i = 1:size(matrix1,1)
     for j = 1:size(matrix2,1)
         if matrix1(i,1) == matrix2(j,1)
            myidx = [ myidx ; [i,j]] ;
         end
     end
 end
 % Indices which you need
 [pos1(myidx(:,1)) pos2(myidx(:,2))]
 % Get new matrix 
 newmatrix = zeros(size(myidx,1),7) ;  % Initialize 
 for i = 1:size(myidx,1)
     newmatrix(i,:) = [matrix1(myidx(i,1),1:end) matrix2(myidx(i,2),2:end)] ;
 end