def _poa_sky_diffuse_pv(f_x, dhi, vf_shade_sky_integ, vf_noshade_sky_integ):
    """
    Sky diffuse POA from integrated view factors combined for both shaded and
    unshaded parts of the surface.

    Parameters
    ----------
    f_x : numeric
        Fraction of row slant height from the bottom that is shaded. [unitless]
    dhi : numeric
        Diffuse horizontal irradiance (DHI). [W/m^2]
    vf_shade_sky_integ : numeric
        Integrated view factor from the shaded part of the row to the sky.
        [unitless]
    vf_noshade_sky_integ : numeric
        Integrated view factor from the unshaded part of the row to the sky.
        [unitless]

    Returns
    -------
    poa_sky_diffuse_pv : numeric
        Total sky diffuse irradiance incident on the PV surface. [W/m^2]
    """
    return dhi * (f_x * vf_shade_sky_integ + (1 - f_x) * vf_noshade_sky_integ)