Method exec

src/org/apache/pig/builtin/COV.java:190–236

(Tuple input)

        }
        
        @Override
        public DataBag exec(Tuple input) throws IOException {
            if (input == null || input.size() == 0)
                return null;
            
            DataBag output = DefaultBagFactory.getInstance().newDefaultBag();
            int count = 0;
            
            //for each pair of input schema combined contain 2 member. first member
            //is tuple containing sum_x,sum_y,sum_x_y and second is number of tuples 
            //from which it is calculated . So if arity of combined is n then total 
            //number of schemas would be root of x*x - x - n =0 
            
            try{
                Tuple combined = combine((DataBag)input.get(0));    
                int totalSchemas=2;
                while(totalSchemas*(totalSchemas-1)<combined.size()){
                    totalSchemas++;
                }
                for(int i=0;i<totalSchemas;i++){
                    for(int j=i+1;j<totalSchemas;j++){
                        Tuple result = TupleFactory.getInstance().newTuple(3);
                        if(flag){
                            result.set(0, schemaName.elementAt(i));
                            result.set(1, schemaName.elementAt(j));
                        }
                        else{
                            result.set(0, "var"+i);
                            result.set(1, "var"+j);
                        }
                        Tuple tup = (Tuple)combined.get(count);
                        double tempCount = (Double)combined.get(count+1);
                        double sum_x_y = (Double)tup.get(0);
                        double sum_x = (Double)tup.get(1);
                        double sum_y = (Double)tup.get(2);
                        double covar = (tempCount*sum_x_y - sum_x*sum_y)/(tempCount*tempCount);
                        result.set(2, covar);
                        output.add(result);
                        count+=2;
                    }
                }
            }catch(Exception e){
                throw new IOException("Caught exception in COV.Intermed", e);
            }

            return output;
        }
    }

    /**