def ndwi(swir, green):
    """
    Compute Vegetation Index from SWIR and GREEN bands

        NDWI = \\frac { GREEN - SWIR } { GREEN + SWIR }

    :param swir:    Swir band
    :param green:   Green band
    :return:        NDWI
    """
    return (green-swir) / (green+swir)