Plots mean period wise returns for factor quantiles.

    Parameters
    ----------
    mean_ret_by_q : pd.DataFrame
        DataFrame with quantile, (group) and mean period wise return values.
    by_group : bool
        Disaggregated figures by group.
    ylim_percentiles : tuple of integers
        Percentiles of observed data to use as y limits for plot.
    ax : matplotlib.Axes, optional
        Axes upon which to plot.

    Returns
    -------
    ax : matplotlib.Axes
        The axes that were plotted on.

def plot_quantile_returns_bar(mean_ret_by_q,
                              by_group=False,
                              ylim_percentiles=None,
                              ax=None):
    """
    Plots mean period wise returns for factor quantiles.

    Parameters
    ----------
    mean_ret_by_q : pd.DataFrame
        DataFrame with quantile, (group) and mean period wise return values.
    by_group : bool
        Disaggregated figures by group.
    ylim_percentiles : tuple of integers
        Percentiles of observed data to use as y limits for plot.
    ax : matplotlib.Axes, optional
        Axes upon which to plot.

    Returns
    -------
    ax : matplotlib.Axes
        The axes that were plotted on.
    """

    mean_ret_by_q = mean_ret_by_q.copy()

    if ylim_percentiles is not None:
        ymin = (np.nanpercentile(mean_ret_by_q.values,
                                 ylim_percentiles[0]) * DECIMAL_TO_BPS)
        ymax = (np.nanpercentile(mean_ret_by_q.values,
                                 ylim_percentiles[1]) * DECIMAL_TO_BPS)
    else:
        ymin = None
        ymax = None

    if by_group:
        num_group = len(
            mean_ret_by_q.index.get_level_values('group').unique())

        if ax is None:
            v_spaces = ((num_group - 1) // 2) + 1
            f, ax = plt.subplots(v_spaces, 2, sharex=False,
                                 sharey=True, figsize=(18, 6 * v_spaces))
            ax = ax.flatten()

        for a, (sc, cor) in zip(ax, mean_ret_by_q.groupby(level='group')):
            (cor.xs(sc, level='group')
                .multiply(DECIMAL_TO_BPS)
                .plot(kind='bar', title=sc, ax=a))

            a.set(xlabel='', ylabel='Mean Return (bps)',
                  ylim=(ymin, ymax))

        if num_group < len(ax):
            ax[-1].set_visible(False)

        return ax

    else:
        if ax is None:
            f, ax = plt.subplots(1, 1, figsize=(18, 6))

        (mean_ret_by_q.multiply(DECIMAL_TO_BPS)
            .plot(kind='bar',
                  title="Mean Period Wise Return By Factor Quantile", ax=ax))
        ax.set(xlabel='', ylabel='Mean Return (bps)',
               ylim=(ymin, ymax))

        return ax