
{{alias}}( W[, mx, my] )
    Returns an accumulator function which incrementally computes a moving
    sample Pearson product-moment correlation distance.

    The correlation distance is defined as one minus the Pearson product-moment
    correlation coefficient and, thus, resides on the interval [0,2].

    However, due to limitations inherent in representing numeric values using
    floating-point format (i.e., the inability to represent numeric values with
    infinite precision), the correlation distance between perfectly correlated
    random variables may *not* be `0` or `2`. In fact, the correlation distance
    is *not* guaranteed to be strictly on the interval [0,2]. Any computed
    distance should, however, be within floating-point roundoff error.

    The `W` parameter defines the number of values over which to compute the
    moving sample correlation distance.

    If provided values, the accumulator function returns an updated moving
    sample correlation distance. If not provided values, the accumulator
    function returns the current moving sample correlation distance.

    As `W` (x,y) pairs 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.

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

    mx: number (optional)
        Known mean.

    my: number (optional)
        Known mean.

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

    Examples
    --------
    > var accumulator = {{alias}}( 3 );
    > var d = accumulator()
    null
    > d = accumulator( 2.0, 1.0 )
    1.0
    > d = accumulator( -5.0, 3.14 )
    ~2.0
    > d = accumulator( 3.0, -1.0 )
    ~1.925
    > d = accumulator( 5.0, -9.5 )
    ~1.863
    > d = accumulator()
    ~1.863

    See Also
    --------

