Full factorial

This script is similar to fullfact, however instead of number of levels, value of levels are required as input  
usage: des_mat = full_fact([-1 1],[100 200 300],[1:4]);  
 
 arguments: (input)  
 x1,x2, x3- variable levels either in row or column vector. These are  
 not number of levels but the levels itself  
   
arguments: (output)  
 des_mat - mxn m= total number of designs (product of all levels) and  
          n is number of variables  
           The first column shows all the first variable levels, second  
           column shows second variable levels and so on.  
   
Example usage:  
 x1=[-1 1];x2=[100:100:300];  
 des_mat = full_fact(x1,x2) % OR  
 des_mat = full_fact([-1 1],[100:100:300])  
 des_mat =  
    -1 100  
    -1 200  
    -1 300  
     1 100  
     1 200  
     1 300