
{{alias}}( W[, mean] )
    Returns an accumulator function which incrementally computes a moving
    corrected sample standard deviation, ignoring NaN values.

    The `W` parameter defines the number of values over which to compute the
    moving corrected sample standard deviation.

    If provided a value, the accumulator function returns an updated moving
    corrected sample standard deviation. If not provided a value, the
    accumulator function returns the current moving corrected sample standard
    deviation.

    As `W` values are needed to fill the window buffer, the first `W-1`
    returned values are calculated from smaller sample sizes. Until the window
    is full, each returned value is calculated from all provided values.

    NaN values are ignored during computation. If provided NaN, the
    accumulator returns the current corrected sample standard deviation.

    Parameters
    ----------
    W: integer
        Window size.

    mean: number (optional)
        Known mean.

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

    Examples
    --------
    > var accumulator = {{alias}}( 3 );
    > var s = accumulator()
    null
    > s = accumulator( 2.0 )
    0.0
    > s = accumulator( NaN )
    0.0
    > s = accumulator( -5.0 )
    ~4.95
    > s = accumulator( 3.0 )
    ~4.36
    > s = accumulator( NaN )
    ~4.36
    > s = accumulator( 5.0 )
    ~5.29
    > s = accumulator()
    ~5.29

    See Also
    --------
    
