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## Struct template lazy_rolling_variance_impl

boost::accumulators::impl::lazy_rolling_variance_impl — Immediate (lazy) calculation of the rolling variance.

## Synopsis

    // In header: <boost/accumulators/statistics/rolling_variance.hpp>

    template<typename Sample>
    struct lazy_rolling_variance_impl : public accumulator_base {
      // types
      typedef numeric::functional::fdiv< Sample, std::size_t, void, void >::result_type result_type;

      // construct/copy/destruct
      lazy_rolling_variance_impl(dont_care);

      // public member functions
      template<typename Args> result_type result(Args const &) const;
    };

## Description

Calculation of sample variance is done as follows, see also http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance. For a rolling window of size , when , the variance is computed according to the formula

Equation 1.7.

When , the sample variance over the window becomes:

Equation 1.8.

### `lazy_rolling_variance_impl` public construct/copy/destruct

1.     lazy_rolling_variance_impl(dont_care);

### `lazy_rolling_variance_impl` public member functions

1.     template<typename Args> result_type result(Args const & args) const;