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

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

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

    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 r = accumulator()
    null
    > r = accumulator( 2.0, 1.0 )
    0.0
    > r = accumulator( -5.0, 3.14 )
    ~-1.0
    > r = accumulator( 3.0, -1.0 )
    ~-0.925
    > r = accumulator( 5.0, -9.5 )
    ~-0.863
    > r = accumulator()
    ~-0.863

    See Also
    --------

