/guava/guava/src/com/google/common/math/PairedStatsAccumulator.java
yStats.add( y) ;xStats.add( x) ;
xStats.add ( x ) ;
@ElementTypesAreNonnullByDefault public final class PairedStatsAccumulator { private final StatsAccumulator xStats = new StatsAccumulator(); private final StatsAccumulator yStats = new StatsAccumulator(); private double sumOfProductsOfDeltas = 0.0; public void add(double x, double y) { <extra_id_0> if (isFinite(x) && isFinite(y)) { if (xStats.count() > 1) { sumOfProductsOfDeltas += (x - xStats.mean()) * (y - yStats.mean()); } } else { sumOfProductsOfDeltas = NaN;