question: public static Range iterateZBounds ( XYZDataset dataset , boolean includeInterval ) { double minimum = Double . POSITIVE_INFINITY ; double maximum = Double . NEGATIVE_INFINITY ; int seriesCount = dataset . getSeriesCount ( ) ; for ( int series = 0 ; series < seriesCount ; series ++ ) { int itemCount = dataset . getItemCount ( series ) ; for ( int item = 0 ; item < itemCount ; item ++ ) { double value = dataset . getZValue ( series , item ) ; if ( ! Double . isNaN ( value ) ) { minimum = Math . min ( minimum , value ) ; maximum = Math . max ( maximum , value ) ; } } } if ( minimum == Double . POSITIVE_INFINITY ) { return null ; } else { return new Range ( minimum , maximum ) ; } }
target:  Iterates over the data items of the xyz dataset to find the z-dimension bounds.