question: public static TDoubleDoubleHashMap createCumulativeHistogram ( TDoubleDoubleHashMap histogram ) { double [ ] keys = histogram . keys ( ) ; Arrays . sort ( keys ) ; double sum = 0 ; for ( double key : keys ) { double val = histogram . get ( key ) ; sum += val ; histogram . put ( key , sum ) ; } return histogram ; }
target:  Creates a cumulative histogram where each bin height is the sum of the previous bin's height and the current bin's height.