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## Struct template weighted_variance_impl

boost::accumulators::impl::weighted_variance_impl — Iterative calculation of variance of weighted samples.

## Synopsis

    template<typename Sample, typename Weight, typename MeanFeature, typename Tag>
    struct weighted_variance_impl {
      // types
      typedef numeric::functional::multiplies< Sample, Weight >::result_type       weighted_sample;
      typedef numeric::functional::average< weighted_sample, Weight >::result_type result_type;

      // construct/copy/destruct
      template<typename Args> weighted_variance_impl(Args const &);

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

## Description

Iterative calculation of variance of weighted samples:

Equation 1.43.

where is the sum of the weights and the estimate of the mean of the weighted smaples. Note that the sample variance is not defined for .

### `weighted_variance_impl` public construct/copy/destruct

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

### `weighted_variance_impl` public member functions

1.     template<typename Args> void operator()(Args const & args) ;

2.     result_type result(dont_care) const;