{{alias}}( [out] )
    Returns an accumulator function which incrementally computes an arithmetic
    mean and unbiased sample variance.

    If provided a value, the accumulator function returns updated accumulated
    values. If not provided a value, the accumulator function returns the
    current accumulated values.

    If provided `NaN`, the accumulated values are equal to `NaN` for all future
    invocations.

    Parameters
    ----------
    out: Array|TypedArray (optional)
        Output array.

    Returns
    -------
    acc: Function
        Accumulator function.

    Examples
    --------
    > var accumulator = {{alias}}();
    > var mv = accumulator()
    null
    > mv = accumulator( 2.0 )
    [ 2.0, 0.0 ]
    > mv = accumulator( -5.0 )
    [ -1.5, 24.5 ]
    > mv = accumulator( 3.0 )
    [ 0.0, 19.0 ]
    > mv = accumulator( 5.0 )
    [ 1.25, ~18.92 ]
    > mv = accumulator()
    [ 1.25, ~18.92 ]

    See Also
    --------