Use Sturges' formula to determine number of bins.

    See https://en.wikipedia.org/wiki/Histogram#Sturges'_formula
    or https://doi.org/10.1080%2F01621459.1926.10502161

    Parameters
    ----------
    dataset: xarray.DataSet
        Must have the `draw` dimension

    mult: float
        Used to scale the number of bins up or down. Default is 1 for Sturges' formula.

    Returns
    -------
    int
        Number of bins to use

def _sturges_formula(dataset, mult=1):
    """Use Sturges' formula to determine number of bins.

    See https://en.wikipedia.org/wiki/Histogram#Sturges'_formula
    or https://doi.org/10.1080%2F01621459.1926.10502161

    Parameters
    ----------
    dataset: xarray.DataSet
        Must have the `draw` dimension

    mult: float
        Used to scale the number of bins up or down. Default is 1 for Sturges' formula.

    Returns
    -------
    int
        Number of bins to use
    """
    return int(np.ceil(mult * np.log2(dataset.draw.size)) + 1)