question: public static Range iterateToFindZBounds ( XYZDataset dataset , List visibleSeriesKeys , Range xRange , boolean includeInterval ) { ParamChecks . nullNotPermitted ( dataset , "dataset" ) ; ParamChecks . nullNotPermitted ( visibleSeriesKeys , "visibleSeriesKeys" ) ; ParamChecks . nullNotPermitted ( xRange , "xRange" ) ; double minimum = Double . POSITIVE_INFINITY ; double maximum = Double . NEGATIVE_INFINITY ; Iterator iterator = visibleSeriesKeys . iterator ( ) ; while ( iterator . hasNext ( ) ) { Comparable seriesKey = ( Comparable ) iterator . next ( ) ; int series = dataset . indexOf ( seriesKey ) ; int itemCount = dataset . getItemCount ( series ) ; for ( int item = 0 ; item < itemCount ; item ++ ) { double x = dataset . getXValue ( series , item ) ; double z = dataset . getZValue ( series , item ) ; if ( xRange . contains ( x ) ) { if ( ! Double . isNaN ( z ) ) { minimum = Math . min ( minimum , z ) ; maximum = Math . max ( maximum , z ) ; } } } } if ( minimum == Double . POSITIVE_INFINITY ) { return null ; } else { return new Range ( minimum , maximum ) ; } }
target:  Returns the range of z-values in the specified dataset for the data items belonging to the visible series and with x-values in the given range.