docs: private double computeKappa(int[] y1,int[] y2){
      	
      	int m=y1.length;
      	
      	double theta1=0;
      	double counts[][]=new double[2][this.modelContext.numClasses()];
      	
      	for (int i=0;i<m;i++){
  	    
      		if (y1[i]==y2[i])
  	    		theta1=theta1+1;
  	    	
  	    	counts[0][y1[i]]=counts[0][y1[i]]+1;
  	    	counts[1][y2[i]]=counts[1][y2[i]]+1;
  	    		
      	}
  	    
      	theta1=theta1/m;
  
      	double theta2=0;
      	
      	for(int i=0;i<this.modelContext.numClasses();i++)
      		theta2+=counts[0][i]/m*counts[1][i]/m;
      	
      	if (theta1==theta2 && theta2==1)
      		return 1;
      	
      	return (theta1-theta2)/(1-theta2);
      }