 Usage:  cross=crosstable(x{,xvars})  
 
 Input:

  x                      n x p matrix, the columns correspond to the variables. 
                         
  xvars                  optional, p x 1 string vector, variable names. 
                         
 Output:

  cross                  string output, containing all crosstables of each 
                         combinations of columns of x, the result of the 
                         Chi-square independence tests and contingency 
                         coefficients. 
                         
--------------------------------------------------------------
(C) MD*TECH Method and Data Technologies, 17.8.2000
