def mean_centroid(candidates):
    """Take the mean of all centroids in set of reference triangles.

    .. note::

       This is used **only** as a helper for :func:`locate_point`.

    Args:
        candidates (List[Tuple[float, float, float, numpy.ndarray]): List of
            4-tuples, each of which has been produced by :func:`locate_point`.
            Each 4-tuple contains

            * Three times centroid ``x``-value
            * Three times centroid ``y``-value
            * "Width" of a parameter space for a surface
            * Control points for a surface

            We only use the first two values, which are triple the desired
            value so that we can put off division by three until summing in
            our average. We don't use the other two values, they are just an
            artifact of the way ``candidates`` is constructed by the caller.

    Returns:
        Tuple[float, float]: The mean of all centroids.
    """
    sum_x = 0.0
    sum_y = 0.0
    for centroid_x, centroid_y, _, _ in candidates:
        sum_x += centroid_x
        sum_y += centroid_y
    denom = 3.0 * len(candidates)
    return sum_x / denom, sum_y / denom
Take the mean of all centroids in set of reference triangles.

    .. note::

       This is used **only** as a helper for :func:`locate_point`.

    Args:
        candidates (List[Tuple[float, float, float, numpy.ndarray]): List of
            4-tuples, each of which has been produced by :func:`locate_point`.
            Each 4-tuple contains

            * Three times centroid ``x``-value
            * Three times centroid ``y``-value
            * "Width" of a parameter space for a surface
            * Control points for a surface

            We only use the first two values, which are triple the desired
            value so that we can put off division by three until summing in
            our average. We don't use the other two values, they are just an
            artifact of the way ``candidates`` is constructed by the caller.

    Returns:
        Tuple[float, float]: The mean of all centroids.