Question

I am curious, what average is obtained from this code snippet? The accumulator is intended to be empty.

boost::accumulators::accumulator_set<
    int,
    boost::accumulators::features<boost::accumulators::tag::mean>
> Accumulator;

int Mean = boost::accumulators::mean(Accumulator);

The average is non-zero when I test it. Is there some way I can tell that the average was taken for an empty data set? Why is the resulting value for “Mean” non-zero?

I was looking around in the documentation for the accumulator library, but was unable to find an answer to this question.

Answer 1

Any value would be a valid mean for an empty set of values. That is x * 0 = 0 holds for any x.

You could add a count feature to your accumulator_set and query it to see if its 0.