question: public static Range findStackedRangeBounds ( CategoryDataset dataset , KeyToGroupMap map ) { ParamChecks . nullNotPermitted ( dataset , "dataset" ) ; boolean hasValidData = false ; Range result = null ; int [ ] groupIndex = new int [ dataset . getRowCount ( ) ] ; for ( int i = 0 ; i < dataset . getRowCount ( ) ; i ++ ) { groupIndex [ i ] = map . getGroupIndex ( map . getGroup ( dataset . getRowKey ( i ) ) ) ; } int groupCount = map . getGroupCount ( ) ; double [ ] minimum = new double [ groupCount ] ; double [ ] maximum = new double [ groupCount ] ; int categoryCount = dataset . getColumnCount ( ) ; for ( int item = 0 ; item < categoryCount ; item ++ ) { double [ ] positive = new double [ groupCount ] ; double [ ] negative = new double [ groupCount ] ; int seriesCount = dataset . getRowCount ( ) ; for ( int series = 0 ; series < seriesCount ; series ++ ) { Number number = dataset . getValue ( series , item ) ; if ( number != null ) { hasValidData = true ; double value = number . doubleValue ( ) ; if ( value > 0.0 ) { positive [ groupIndex [ series ] ] = positive [ groupIndex [ series ] ] + value ; } if ( value < 0.0 ) { negative [ groupIndex [ series ] ] = negative [ groupIndex [ series ] ] + value ; } } } for ( int g = 0 ; g < groupCount ; g ++ ) { minimum [ g ] = Math . min ( minimum [ g ] , negative [ g ] ) ; maximum [ g ] = Math . max ( maximum [ g ] , positive [ g ] ) ; } } if ( hasValidData ) { for ( int j = 0 ; j < groupCount ; j ++ ) { result = Range . combine ( result , new Range ( minimum [ j ] , maximum [ j ] ) ) ; } } return result ; }
target:  Returns the minimum and maximum values for the dataset's range (y-values), assuming that the series in one category are stacked.