How to calculate aggregates over array with mask in Java?

Question

I have an array of primitives, which can contain Nan values. How do I calculate an aggregate of it? Like, org.apache.commons.math3.stat.descriptive.moment.Mean gives Nan as an output. Of course, I can code this by hand, but maybe an elegant and efficient solution exists already?

Joni · Accepted Answer · 2020-04-06 12:24:09Z

1

If you use the stream API, you can use the filter function to remove NaN and other "irregular" values when you compute the statistics.

double[] array = {1, Double.NaN, 3};
DoubleSummaryStatistics statistics = Arrays.stream(array).filter(Double::isFinite).summaryStatistics();
double average = statistics.getAverage(); // 2.0
double sum = statistics.getSum(); // 4.0

answered Apr 6, 2020 at 12:24

Joni

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3 Comments

Alexey Mints Over a year ago

Thanks a lot! I'll give it a try.

Alexey Mints Over a year ago

Btw, how numerically efficient is stream API? I have to call this function many (millions) of times, so it is significant not to slow things down...

Joni Over a year ago

Try and see. If it turns out to be a bottle neck later on it's easy to replace with something else

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